MoritzLost

Building a reusable function to generate responsive images

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Hello there,
I've started using ProcessWire at work a while ago and I have been really enjoying building modular, clean and fast sites based on the CMS (at work, I usually post as @schwarzdesign). While building my first couple of websites with ProcessWire, I have written some useful helper functions for repetitive tasks. In this post I want to showcase and explain a particular function that generates a responsive image tag based on an image field, in the hope that some of you will find it useful :)

I'll give a short explanation of responsive images and then walk through the different steps involved in generating the necessary markup & image variations. I want to keep this beginner-friendly, so most of you can probably skip over some parts.

What are responsive images

I want to keep this part short, there's a really good in-depth article about responsive images on MDN if you are interested in the details. The short version is that a responsive image tag is simply an <img>-tag that includes a couple of alternative image sources with different resolutions for the browser to choose from. This way, smaller screens can download the small image variant and save data, whereas high-resolution retina displays can download the extra-large variants for a crisp display experience. This information is contained in two special attributes:

  • srcset - This attribute contains a list of source URLs for this image. For each source, the width of the image in pixels is specified.
  • sizes - This attribute tells the browser how wide a space is available for the image, based on media queries (usually the width of the viewport).

This is what a complete responsive image tag may look like:

<img srcset="/site/assets/files/1015/happy_sheep_07.300x0.jpg 300w,
            /site/assets/files/1015/happy_sheep_07.600x0.jpg 600w,
            /site/assets/files/1015/happy_sheep_07.900x0.jpg 900w,
            /site/assets/files/1015/happy_sheep_07.1200x0.jpg 1200w,
            /site/assets/files/1015/happy_sheep_07.1800x0.jpg 1800w,
            /site/assets/files/1015/happy_sheep_07.2400x0.jpg 2400w"
    sizes="(min-width: 1140px) 350px,
            (min-width: 992px) 480px,
            (min-width: 576px) 540px,
            100vw"
    src="/site/assets/files/1015/happy_sheep_07.1200x0.jpg" alt="One sheep">

This tells the browser that there are six different sources for this image available, ranging from 300px to 2400px wide variants (those are all the same image, just in different resolutions). It also tells the browser how wide the space for the image will be:

  • 350px for viewports >= 1140px
  • 480px for viewports >= 992px
  • 540px for viewports >= 576px
  • 100vw (full viewport width) for smaller viewports

The sizes queries are checked in order of appearance and the browser uses the first one that matches. So now, the browser can calculate how large the image needs to be and then select the best fit from the srcset list to download. For browsers that don't support responsive images, a medium-sized variant is included as the normal src-Attribute.

This is quite a lot of markup which I don't want to write by hand every time I want to place an image in a ProcessWire template. The helper function will need to generate both the markup and the variations of the original image.

Building a reusable responsive image function

Let's start with a function that takes two parameters: a Pageimage object and a standard width. Every time you access an image field through the API in a template (e.g. $page->my_image_field), you get a Pageimage object. Let's start with a skeleton for our function:

function buildResponsiveImage(
    Pageimage $img,
    int $standard_width
): string {
    $default_img = $img->maxWidth($standard_width);
    return '<img src="' . $default_img->url() . '" alt="' . $img->description() . '">';
}

// usage example
echo buildResponsiveImage($page->my_image_field, 1200);

This is already enough for a normal img tag (and it will serve as a fallback for older browsers). Now let's start adding to this, trying to keep the function as flexible and reusable as possible.

Generating alternate resolutions

We want to add a parameter that will allow the caller to specify in what sizes the alternatives should be generated. We could just accept an array parameter that contains the desired sizes as integers. But that is not very extendible, as we'll need to specify those sizes in each function call and change them all if the normal size of the image in the layout changes. Instead, we can use an array of factors; that will allow us to set a reasonable default, and still enable us to manually overwrite it. In the following, the function gets an optional parameter $variant_factor.

// get the original image in full size
$original_img = $img->getOriginal() ?? $img;

// the default image for the src attribute, it wont be upscaled
$default_image = $original_img->width($standard_width, ['upscaling' => false]);

// the maximum size for our generated images
$full_image_width = $original_img->width();

// fill the variant factors with defaults if not set
if (empty($variant_factors)) {
    $variant_factors = [0.25, 0.5, 0.75, 1, 1.5, 2];
}

// build the srcset attribute string, and generate the corresponding widths
$srcset = [];
foreach ($variant_factors as $factor) {
    // round up, srcset doesn't allow fractions
    $width = ceil($standard_width * $factor);
    // we won't upscale images
    if ($width <= $full_image_width) {
        $srcset[] = $original_img->width($width)->url() . " {$width}w";
    }
}
$srcset = implode(', ', $srcset);

// example usage
echo buildResponsiveImage($page->my_image_field, 1200, [0.4, 0.5, 0.6, 0.8, 1, 1.25, 1.5, 2]);

Note that for resizing purposes, we want to get the original image through the API first, as we will generate some larger alternatives of the images for retina displays. We also don't want to generate upscaled versions of the image if the original image isn't wide enough, so I added a constraint for that.

The great thing about the foreach-loop is that it generates the markup and the images on the server at the same time. When we call $original_img->width($width), ProcessWire automatically generates a variant of the image in that size if it doesn't exist already. So we need to do little work in terms of image manipulation.

Generating the sizes attribute markup

For this, we could build elaborate abstractions of the normal media queries, but for now, I've kept it very simple. The sizes attribute is defined through another array parameter that contains the media queries as strings in order of appearance.

$sizes_attribute = implode(', ', $sizes_queries);

The media queries are always separated by commas followed by a space character, so that part can be handled by the function. We'll still need to manually write the media queries when calling the function though, so that is something that can be improved upon.

Finetuning & improvements

This is what the function looks like now:

function buildResponsiveImage(
    Pageimage $img,
    int $standard_width,
    array $sizes_queries,
    ?array $variant_factors = []
): string {

    // get the original image in full size
    $original_img = $img->getOriginal() ?? $img;
    
    // the default image for the src attribute, it wont be upscaled
    $default_image = $original_img->width($standard_width, ['upscaling' => false]);

    // the maximum size for our generated images
    $full_image_width = $original_img->width();

    // fill the variant factors with defaults if not set
    if (empty($variant_factors)) {
        $variant_factors = [0.25, 0.5, 0.75, 1, 1.5, 2];
    }

    // build the srcset attribute string, and generate the corresponding widths
    $srcset = [];
    foreach ($variant_factors as $factor) {
        // round up, srcset doesn't allow fractions
        $width = ceil($standard_width * $factor);
        // we won't upscale images
        if ($width <= $full_image_width) {
            $srcset[] = $original_img->width($width)->url() . " {$width}w";
        }
    }
    $srcset = implode(', ', $srcset);

    return '<img src="' . $default_img->url() . '" alt="' . $img->description() . '" sizes="' . $sizes_attribute . '" srcset="' . $srcset . '">';
}

It contains all the part we need, but there are some optimizations to make.

First, we can make the $sizes_queries parameters optional. The sizes attribute default to 100vw (so the browser will always download an image large enough to fill the entire viewport width). This isn't optimal as it wastes bandwidth if the image doesn't fill the viewport, but it's good enough as a fallback.

We can also make the width optional. When I have used this function in a project, the image I passed in was oftentimes already resized to the correct size. So we can make $standard_width an optional parameter that defaults to the width of the passed image.

if (empty($standard_width)) {
    $standard_width = $img->width();
}

Finally, we want to be able to pass in arbitrary attributes that will be added to the element. For now, we can just add a parameter $attributes that will be an associative array of attribute => value pairs. Then we need to collapse those into html markup.

$attr_string = implode(
    ' ',
    array_map(
        function($attr, $value) {
            return $attr . '="' . $value . '"';
        },
        array_keys($attributes),
        $attributes
    )
);

This will also allow for some cleanup in the way the other attributes are generated, as we can simply add those to the $attributes array along the way.

Here's the final version of this function with typehints and PHPDoc. Feel free to use this is your own projects.

/**
* Builds a responsive image element including different resolutions
* of the passed image and optionally a sizes attribute build from
* the passed queries.
*
* @param \Processwire\Pageimage $img The base image.
* @param int|null $standard_width The standard width for this image. Use 0 or NULL to use the inherent size of the passed image.
* @param array|null $attributes Optional array of html attributes.
* @param array|null $sizes_queries The full queries and sizes for the sizes attribute.
* @param array|null $variant_factors The multiplication factors for the alternate resolutions.
* @return string
*/
function buildResponsiveImage(
    \Processwire\Pageimage $img,
    ?int $standard_width = 0,
    ?array $attributes = [],
    ?array $sizes_queries = [],
    ?array $variant_factors = []
): string {

    // if $attributes is null, default to an empty array
    $attributes = $attributes ?? [];

    // if the standard width is empty, use the inherent width of the image
    if (empty($standard_width)) {
        $standard_width = $img->width();
    }

    // get the original image in full size
    $original_img = $img->getOriginal() ?? $img;

    // the default image for the src attribute, it wont be
    // upscaled if the desired width is larger than the original
    $default_image = $original_img->width($standard_width, ['upscaling' => false]);

    // we won't create images larger than the original
    $full_image_width = $original_img->width();

    // fill the variant factors with defaults
    if (empty($variant_factors)) {
        $variant_factors = [0.25, 0.5, 0.75, 1, 1.5, 2];
    }

    // build the srcset attribute string, and generate the corresponding widths
    $srcset = [];
    foreach ($variant_factors as $factor) {
        // round up, srcset doesn't allow fractions
        $width = ceil($standard_width * $factor);
        // we won't upscale images
        if ($width <= $full_image_width) {
            $srcset[] = $original_img->width($width)->url() . " {$width}w";
        }
    }
    $attributes['srcset'] = implode(', ', $srcset);

    // build the sizes attribute string
    if ($sizes_queries) {
        $attributes['sizes'] = implode(', ', $sizes_queries);
    }

    // add src fallback and alt attribute
    $attributes['src'] = $default_image->url();
    if ($img->description()) {
        $attriutes['alt'] = $img->description();
    }
 
    // implode the attributes array to html markup
    $attr_string = implode(' ', array_map(function($attr, $value) {
        return $attr . '="' . $value . '"';
    }, array_keys($attributes), $attributes));

    return "<img ${attr_string}>";

}

Example usage with all arguments:

echo buildResponsiveImage(
    $page->testimage,
    1200,
    ['class' => 'img-fluid', 'id' => 'photo'],
    [
        '(min-width: 1140px) 350px',
        '(min-width: 992px) 480px',
        '(min-width: 576px) 540px',
        '100vw'
    ],
    [0.4, 0.5, 0.6, 0.8, 1, 1.25, 1.5, 2]
);

Result:

<img class="img-fluid" id="photo" srcset="/site/assets/files/1/sean-pierce-1053024-unsplash.480x0.jpg 480w, /site/assets/files/1/sean-pierce-1053024-unsplash.600x0.jpg 600w, /site/assets/files/1/sean-pierce-1053024-unsplash.720x0.jpg 720w, /site/assets/files/1/sean-pierce-1053024-unsplash.960x0.jpg 960w, /site/assets/files/1/sean-pierce-1053024-unsplash.1200x0.jpg 1200w, /site/assets/files/1/sean-pierce-1053024-unsplash.1500x0.jpg 1500w, /site/assets/files/1/sean-pierce-1053024-unsplash.1800x0.jpg 1800w, /site/assets/files/1/sean-pierce-1053024-unsplash.2400x0.jpg 2400w" sizes="(min-width: 1140px) 350px, (min-width: 992px) 480px, (min-width: 576px) 540px, 100vw" src="/site/assets/files/1/sean-pierce-1053024-unsplash.1200x0.jpg" alt="by Sean Pierce">

Now this is actually too much functionality for one function; also, some of the code will be exactly the same for other, similar helper functions. If some of you are interested, I'll write a second part on how to split this into multiple smaller helper functions with some ideas on how to build upon it. But this has gotten long enough, so yeah, I hope this will be helpful or interesting to some of you :)

Also, if you recognized any problems with this approach, or can point out some possible improvements, let me know. Thanks for reading!

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hi @MoritzLost , thanks for the detailed tutorial! do you know this module?

If yes, you might elaborate what is different on your approach 🙂 

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Hi, thank you for the write up. 👍

For me it looks you found the right balance for beginners and experienced users.

A following second part would be very nice and useful.

Additionally to that, if you don't mind, I would be interested in a third part too. This one should cover how the function(s) recognize or act upon changes of a focus point or zoom value, if used. 

Does it recognize it, and recreate all variations? 

Do you also include / provide or already use a function to remove exactly the previously created variations? Maybe useful during developing a site, when my first used sizes need to be adjusted. (Otherwise I would have a lot unused variations). If you don't use this already, I think it could be done very easy by using a suffix for the variations. 

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20 hours ago, bernhard said:

hi @MoritzLost , thanks for the detailed tutorial! do you know this module?

If yes, you might elaborate what is different on your approach 🙂 

Hi Bernard, I didn't know that module, looks interesting as well 🙂 Well, it's a different approach in that I'm not using javascript and instead generate the entire function based on the passed parameters. I'm just using native functionality instead of Javascript, which is good if you don't have to support older browsers. The generation of the srcset and corresponding images seems to be handled in a similar way though, so it comes down to preferences I guess.

20 hours ago, horst said:

Additionally to that, if you don't mind, I would be interested in a third part too. This one should cover how the function(s) recognize or act upon changes of a focus point or zoom value, if used.  

Does it recognize it, and recreate all variations?  

Hi horst, thanks 🙂 I actually don't know how this interacts with changing focus points, my last projects didn't really involve heavy usage of the focus points. I'll need to do some testing, I'll update the function when I get to it.

20 hours ago, horst said:

Do you also include / provide or already use a function to remove exactly the previously created variations? Maybe useful during developing a side, when my first used sizes need to be adjusted. (Otherwise I would have a lot unused variations). If you don't use this already, I think it could be done very easy by using a suffix for the variations. 

For my last projects I just temporarily put $img->removeVariations() in the function and clicked through the site (should be easy to automate based on the sitemap). Though this will be trouble when the editors manually create variations. Hm, using a suffix for the generated images is a good idea, this way they could all be invalidated at once. I haven't used suffixes yet, I'll look into that. Do you have a suggestion on how to modify the function accordingly? 🙂

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21 hours ago, tpr said:

MarkupSrcSet doesn't use JS to generate the markup. I guess the JSON format that misled you, in fact the module was rewritten a year ago, see this post:

https://processwire.com/talk/topic/12981-markupsrcset/?do=findComment&amp;comment=150129

 

I see, in this case I guess it's just two different approaches toward the same goal 🙂 All your examples use the data-srcset attribute to be consumed by lazysizes, though the syntax is identical with the regular srcset attribute, so I'd say at the core the functionality is similar.

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My module was also adding other attributes beforehand, eg classes, but that was too restricting, and IDEs were complaining about missing img attributes. That's why I decided to rewrite it to generate the srcset attribute only that you can use the way you need. It even works with lazysizes bgset attribute that I often use.

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On 9/12/2018 at 8:49 PM, MoritzLost said:

For my last projects I just temporarily put $img->removeVariations() in the function

Yep, it then definetly removes all variations. 🙂

But in some cases it may become handy to use a scalpell instead of a hammer. For example, if you use the same images in different locations, as with centralized image pages, you may have a total of 100 variations but only 7 do belong to your current template.

Just a thought: Maybe a programmatically created suffix, based on the (page | template | imagefield), can be embedded into the variation names? This way, you only need a delete-function that gets passed that suffix, to remove only variations containing it in their names.

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On 9/14/2018 at 9:26 PM, horst said:

Yep, it then definetly removes all variations. 🙂

But in some cases it may become handy to use a scalpell instead of a hammer. For example, if you use the same images in different locations, as with centralized image pages, you may have a total of 100 variations but only 7 do belong to your current template.

Just a thought: Maybe a programmatically created suffix, based on the (page | template | imagefield), can be embedded into the variation names? This way, you only need a delete-function that gets passed that suffix, to remove only variations containing it in their names.

That's a good point, I'll give that a shot!

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@horst I finally got around to test some stuff now regarding the focus points and orphaned image files.

I actually had a problem with the version of the function in my tutorial above; because the function accessed the original image, the generated images always had the same aspect ratio of the original image, instead of the aspect ratio of the image I passed in. So I forewent using the original image for the tests.

As for the focus points, I did some testing on how Processwire handles this. My takeaways (someone correct me if I'm wrong):

  • Image variations are only saved to disk, not to the database. So the only permanent record of an image variation is the physical file on the disk, identified by the appended height and width and suffix string.
  • Whenever I change the focus/zoom of an image and save the page, all variations are automatically regenerated.

In combination with my responsive image function, this actually lead to a curious problem. I uploaded a 1920x1080 image to an image field, then created an 800x800 variation through the API. Then I passed that one into the responsive image function, at this point a couple of square-sized variations were created. However, since I only specified a width, the height-parameter in the filename was set to "0". So when I changed the focus point of that image, the variations were recreated in the original 16/9 format instead of the desired square format.

I'm not sure if this is intentional or a bug, for now I've restructured the responsive image function to take both a width and a height parameter so that the aspect ratio is fixed, and added shortcut functions that only take height / width as an argument. That should solve the focus point problem.

Regarding the cleanup of orphaned files, I'm still not sure if there is an elegant solution. I've added a suffix 'auto_srcset', but the generated images are still spread across multiple folders corresponding to the page id. I feel like cleaning those up all at once would rather be a job for a cleanup script than a single function. Something like the script ryan posted here:

Anyway, I can't posted the updated code right now (I'm in the process of writing a small utility library for which I converted all those helper functions into static object methods), but I'll try to post that second part soon and include the updated functions; I might only get to that after my vacation though.
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Very nice writeup. Thank you for sharing! There are so many different approaches to handling responsive images and it is great to see how others do it. Would love to see more approaches from others here, too.

To get the concept of responsive images, I read the anatomy of responsive images which explains them very well. Then I used to implement a quite similar approach to @MoritzLost for some time utilizing the MarkupSrcset module and also my own functions. Until I stumbled upon an article about creating responsive images  which shows an approach that I now prefer.

In this approach you go through all your different images in the finished layout and determine their exact respective size at your breakpoints. Then you build srcset and sizes attributes for those exact values. So there is no more approximation using scaling factors. You get exactly the amount of images at the sizes you need them.

I pass an array with the breakpoints and the required sizes for that breakpoint and build srcset and sizes from that array. Here's the code:

/**
 * Builds responsive img tag with srcset and sizes attributes
 * @param \Processwire\Pageimage $img
 * @param array $breakpointsizes array of associative arrays that describe media min breakpoints and width/height of images from the respective
 * breakpoint to the next
 * Example:
 * $breakpointSizes = [
 *   ['bp' => 320, 'sz' => [500, 0]],
 *   ['bp' => 576, 'sz' => [992, 0]],
 *   ['bp' => 992, 'sz' => [690, 0]]
 *   ['bp' => 1200, 'sz' => [835, 0]]
 * ];
 * @return string 
 */
function renderImageResponsive($img, $breakpointSizes) {

  $imgSrc = $img->url; // use original image as fallback src
  $alt = ($img->description) ? $img->description : $img->page->title; // if no description use page title 

  // construct sizes attribute
  $sizes = array();
  foreach(array_reverse($breakpointSizes) as $bs) {
    $sizes[] = "(min-width:{$bs['bp']}px) {$bs['sz'][0]}px";
  }
  $sizes = implode(', ', $sizes) . ', 100vw';

  // construct srcset attribute
  $srcSet = array();
  foreach($breakpointSizes as $bs) {
    $srcSet[] = $img->size($bs['sz'][0], $bs['sz'][1])->url . " {$bs['sz'][0]}w";
  }
  $srcSet = implode(', ', $srcSet);

  return "<img class='img-fluid' src='{$imgSrc}' srcset='{$srcSet}' sizes='{$sizes}' alt='{$alt}'>";

}

Obviously it does not account for Retina which needs to be added. I will also extend my function to add support for other attributes like you showed it. That is a great idea.

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Quote

no more approximation using scaling factors. You get exactly the amount of images at the sizes you need them. 

Thanks for sharing this. This opens up a better way than the usual sandwich responsive style.

Until now I used this css padding-bottom a lot to keep images truly responsive on all devices.

 

.your class {
background-image: url(/site/assets/files/1014/background.jpg);
background-size: 100%;
padding-bottom: x%;
background-repeat: no-repeat;
}

 

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      public static function startTag( string $element, ?array $attributes = [] ): string { $attribute_string = self::attributes($attributes, true); return "<{$element}{$attribute_string}>"; } public static function endTag(string $element): string { return "</{$element}>"; } Of course, the startTag function builds on the existing function to generate the attributes. Note that a start tag is identical with a standalone tag (i.e. a void HTML element such as the img tag).
      At this point, it's also trivial to write a function that builds a complete element, including start and end tag as well as the enclosed content.
      public static function element( string $element, ?string $content = null, array $attributes = [], $self_closing = false ): string { if ($self_closing) { return self::startTag($element, $attributes); } else { return self::startTag($element, $attributes) . $content . self::endTag($element); } } Note that while this function does take several arguments, all except the first have reasonable default values, so usually the caller will only have to pass two or three of them. Some examples:
      echo Html::startTag('hr'); // <hr> echo Html::element('a', 'My website', ['href' => 'http://herebedragons.world']); // <a href="http://herebedragons.world">My website</a> Image tags
      Those functions make for a solid foundation to build any type of HTML element markup. Based on the type, the functions can accept more specific arguments to be easier to use. For example, the previous link example could be simplified by writing a link function that accepts a link text and an href value, since those are needed for any link:
      public static function link( string $url, ?string $text = null, array $attributes = [] ): string { // use url as text if no text was passed $text = $text ?? $url; $attributes['href'] = $url; return self::element('a', $text, $attributes); } Anyway, for our image markup function, we'll take a Pageimage object as an argument instead, since most images we will use in a ProcessWire template will come from the ProcessWire API. Since all ProcessWire image fields have a description field by default, we can use that description as the alt attribute, which is good practice for accessibility.
      public static function image(Pageimage $img, array $attributes = []): string { $attributes['src'] = $img->url(); // use image description as alt text, unless specified in $attributes if (empty($attributes['alt']) && !empty($img->description())) { $attributes['alt'] = $img->description(); } return self::selfClosingElement('img', $attributes); } Pretty simple. Note that the alt attribute can still be manually overridden by the caller by including it in the $attributes array.
      Responsive images
      Now, the responsive image function can be shortened by building on this function in turn. Optimally, the three distinct tasks this performs (see above) should be separated into their own functions as well, however in practice I haven't seen much need for this. Also, this post is plenty long already, so ...
      public static function imageResponsive( Pageimage $img, ?int $standard_width = 0, ?int $standard_height = 0, ?array $attributes = [], ?array $sizes_queries = [], array $variant_factors = [0.25, 0.5, 0.75, 1, 1.5, 2] ): string { // use inherit dimensions of the passed image if standard width/height is empty if (empty($standard_width)) { $standard_width = $img->width(); } if (empty($standard_height)) { $standard_height = $img->height(); } $suffix = 'auto_srcset'; // if $attributes is null, default to an empty array $attributes = $attributes ?? []; // get original image for resizing $original_image = $img->getOriginal() ?? $img; // the default image for the src attribute $default_image = $original_image->size( $standard_width, $standard_height, ['upscaling' => false, 'suffix' => $suffix] ); // build the srcset attribute string, and generate the corresponding widths $srcset = []; foreach ($variant_factors as $factor) { // round up, srcset doesn't allow fractions $width = ceil($standard_width * $factor); $height = ceil($standard_height * $factor); // we won't upscale images if ($width <= $original_image->width() && $height <= $original_image->height()) { $current_image = $original_image->size($width, $height, ['upscaling' => false, 'suffix' => $suffix]); $srcset[] = $current_image->url() . " {$width}w"; } } $attributes['srcset'] = implode(', ', $srcset); // build the sizes attribute string if ($sizes_queries) { $attributes['sizes'] = implode(', ', $sizes_queries); } return self::image($default_image, $attributes); } See my last post for details. Since then, I made some changed to the function I outlined here (thanks to @horst for pointing out some pitfalls with my approach). Most notably:
      The generated images now include a prefix so they can be removed by a cleanup script more easily. The function now accepts a width and a height parameter so that the aspect ratio of the generated images is fixed (reasons for this change are explained here). To get the original functionality back, I also wrote two helper functions that takes only a width/height and fill in the missing parameter based on the aspect ratio of the passed image. The helper functions look like this:
      public static function imageResponsiveByWidth( Pageimage $img, ?int $standard_width = 0, ?array $attributes = [], ?array $sizes_queries = [], array $variant_factors = [0.25, 0.5, 0.75, 1, 1.5, 2] ): string { // automatically fill the height parameter based // on the aspect ratio of the passed image if (empty($standard_width)) { $standard_width = $img->width(); } $factor = $img->height() / $img->width(); $standard_height = ceil($factor * $standard_width); return self::imageResponsive( $img, $standard_width, $standard_height, $attributes, $sizes_queries, $variant_factors ); } Conclusion
      This approach was born out of necessity, since pure PHP templating makes for some messy code. Of course, another approach would be to use a template engine in the first place. However, I didn't want the overhead of installing Twig or Blades for my smaller projects, so for those small to medium-sized projects, I found some helper functions to generate markup and clean up my code to be a helpful addition.
      A small disclaimer, I update those functions pretty frequently while developing with ProcessWire, so it's possible some errors made their way into the versions I posted here that I haven't discovered yet. If you want to use some of the included code in your own projects, make sure to properly test it.
      I'm also working on a small library including those and some other helpers I wrote, I'll post a Github link once it's in a usable stage.
      So this post got way longer than I intended, I hope that some of you still made your way through it and enjoyed it a bit 🙂 If you see some problems or possible improvements to those methods and the general approach, I'd be happy to hear them!
      Complete code for reference
      <?php use \Processwire\Pageimage; class Html { /** * Build a simple element tag with the passed element. * * @param string $element The element/tag name as a string. * @param ?string $content The content of the element (what goes between the tags). * @param ?array $attributes Optional attributes for the element. * @param boolean $self_closing Whether the element is self-closing (i.e. no end tag). $content is ignored if true. * @return string The HTML element markup. */ public static function element( string $element, ?string $content = null, array $attributes = [], $self_closing = false ): string { if ($self_closing) { return self::startTag($element, $attributes); } else { return self::startTag($element, $attributes) . $content . self::endTag($element); } } /** * Builds a start tag for an element (or a self-closing/void element). * * @param string $element * @param array $attributes * @return string The HTML start tag markup. */ public static function startTag( string $element, ?array $attributes = [] ): string { $attribute_string = self::attributes($attributes, true); return "<{$element}{$attribute_string}>"; } /** * Build an end tag for an element. * * @param string $element The HTML end tag markup. * @return void */ public static function endTag(string $element): string { return "</{$element}>"; } /** * Build an HTML attribute string from an array of attributes. Attributes set * to (bool) true will be included as standalone (no attribute value) and left * out if set to (bool) false. * * @param array $attributes Attributes in attribute => value form. * @param bool $leading_space Whether to include a leading space in the attribute string. * @return string The attributes as html markup. */ public static function attributes( array $attributes, bool $leading_space = false ): string { $attr_string = ''; foreach ($attributes as $attr => $val) { if (is_bool($val)) { if ($val) { $attr_string .= " $attr"; } } else { $attr_string .= ' ' . $attr . '="' . $val . '"'; } } if (!$leading_space) { $attr_string = ltrim($attr_string, ' '); } return $attr_string; } /** * Image Functions. */ /** * Build a simple image tag from a Processwire Pageimage object. * * @param Pageimage $img The image to use. * @param array $attributes Optional attributes for the element. * @return string */ public static function image(Pageimage $img, array $attributes = []): string { $attributes['src'] = $img->url(); // use image description as alt text, unless specified in $attributes if (empty($attributes['alt']) && !empty($img->description())) { $attributes['alt'] = $img->description(); } return self::selfClosingElement('img', $attributes); } /** * Builds a responsive image element including different resolutions * of the passed image and optionally a sizes attribute build from * the passed queries. * * @param Pageimage $img The base image. Must be passed in the largest size available. * @param int|null $standard_width The standard width for the generated image. Use NULL to use the inherent size of the passed image. * @param int|null $standard_height The standard height for the generated image. Use NULL to use the inherent size of the passed image. * @param array|null $attributes Optional array of html attributes. * @param array|null $sizes_queries The full queries and sizes for the sizes attribute. * @param array|null $variant_factors The multiplication factors for the alternate resolutions. * @return string */ public static function imageResponsive( Pageimage $img, ?int $standard_width = 0, ?int $standard_height = 0, ?array $attributes = [], ?array $sizes_queries = [], array $variant_factors = [0.25, 0.5, 0.75, 1, 1.5, 2] ): string { // use inherit dimensions of the passed image if standard width/height is empty if (empty($standard_width)) { $standard_width = $img->width(); } if (empty($standard_height)) { $standard_height = $img->height(); } $suffix = 'auto_srcset'; // if $attributes is null, default to an empty array $attributes = $attributes ?? []; // get original image for resizing $original_image = $img->getOriginal() ?? $img; // the default image for the src attribute $default_image = $original_image->size( $standard_width, $standard_height, ['upscaling' => false, 'suffix' => $suffix] ); // build the srcset attribute string, and generate the corresponding widths $srcset = []; foreach ($variant_factors as $factor) { // round up, srcset doesn't allow fractions $width = ceil($standard_width * $factor); $height = ceil($standard_height * $factor); // we won't upscale images if ($width <= $original_image->width() && $height <= $original_image->height()) { $current_image = $original_image->size($width, $height, ['upscaling' => false, 'suffix' => $suffix]); $srcset[] = $current_image->url() . " {$width}w"; } } $attributes['srcset'] = implode(', ', $srcset); // build the sizes attribute string if ($sizes_queries) { $attributes['sizes'] = implode(', ', $sizes_queries); } return self::image($default_image, $attributes); } /** * Shortcut for the responsiveImage function that only takes a width parameter. * Height is automatically generated based on the aspect ratio of the passed image. * * @param Pageimage $img The base image. Must be passed in the largest size available. * @param int|null $standard_width The standard width for this image. Use NULL to use the inherent size of the passed image. * @param array|null $attributes Optional array of html attributes. * @param array|null $sizes_queries The full queries and sizes for the sizes attribute. * @param array|null $variant_factors The multiplication factors for the alternate resolutions. * @return string */ public static function imageResponsiveByWidth( Pageimage $img, ?int $standard_width = 0, ?array $attributes = [], ?array $sizes_queries = [], array $variant_factors = [0.25, 0.5, 0.75, 1, 1.5, 2] ): string { // automatically fill the height parameter based // on the aspect ratio of the passed image if (empty($standard_width)) { $standard_width = $img->width(); } $factor = $img->height() / $img->width(); $standard_height = ceil($factor * $standard_width); return self::imageResponsive( $img, $standard_width, $standard_height, $attributes, $sizes_queries, $variant_factors ); } /** * Shortcut for the responsiveImage function that only takes a height parameter. * Width is automatically generated based on the aspect ratio of the passed image. * * @param Pageimage $img The base image. Must be passed in the largest size available. * @param int|null $standard_height The standard height for this image. Use NULL to use the inherent size of the passed image. * @param array|null $attributes Optional array of html attributes. * @param array|null $sizes_queries The full queries and sizes for the sizes attribute. * @param array|null $variant_factors The multiplication factors for the alternate resolutions. * @return string */ public static function imageResponsiveByHeight( Pageimage $img, ?int $standard_height = 0, ?array $attributes = [], ?array $sizes_queries = [], array $variant_factors = [0.25, 0.5, 0.75, 1, 1.5, 2] ): string { // automatically fill the width parameter based // on the aspect ratio of the passed image if (empty($standard_height)) { $standard_height = $img->height(); } $factor = $img->width() / $img->height(); $standard_width = ceil($factor * $standard_height); return self::imageResponsive( $img, $standard_width, $standard_height, $attributes, $sizes_queries, $variant_factors ); } }  
    • By Guy Verville
      First of all, I'm not an expert on PHP. I recently read about generators and I understand their usefulness in avoiding loading a set of objects into an array to the point of saturating the memory.
      The $pages->find() call is known to be greedy (and slow) when it comes to processing large amounts of pages, because it loads all objects into memory.
      Is there a way to use a generator to avoid this problem? Is there a workaround? I know that $pages->findMany() exists, but it is also called greedy.
      See https://secure.php.net/manual/en/language.generators.php
      Translated with www.DeepL.com/Translator
    • By John W.
      SYNOPSIS
      A little guide to generating an sitemap.xml using (I believe) a script Ryan originally wrote with the addition of being able to optionally exclude child pages from being output in the sitemap.xml file.
      I was looking back on a small project today where I was using a php script to generate an xml file, I believe the original was written by Ryan. Anyway, I needed a quick fix for the script to allow me to optionally exclude children of pages from being included in the sitemap.xml output.
      OVERVIEW
      A good example of this is a site where if you visit /minutes/ a page displays a list of board meetings which includes a title,  date, description and link to download the .pdf file.
      I have a template called minutes and a template called minutes-document. The first page, minutes, when loaded via /minutes/ simply grabs all of its child pages and outputs the name, description and actual path of an uploaded .pdf file for a visitor to download.
      In my back-end I have the template MINUTES and MINUTES-DOCUMENT. Thus:


      So, basically, their employee can login, hover over minutes, click new, then create a new (child) record and name it the date of the meeting e.g. June 3rd, 2016 :

       
      ---------------------------
      OPTIONALLY EXCLUDING CHILDREN - SETUP
      Outputting the sitemap.xml and optionally excluding children that belong to a template.
      The setup of the original script is as follows:
      1. Save the file to the templates folder as sitemap.xml.php
      2. Create a template called sitemap-xml and use the sitemap.xml.php file.
      3. Create a page called sitemap.xml using the sitemap-xml template
       
      Now, with that done you will need to make only a couple of slight modifications that will allow the script to exclude children of a template from output to the sitemap.xml
      1. Create a new checkbox field and name it:   sitemap_exclude_children
      2. Add the field to a template that you want to control whether the children are included/excluded from the sitemap. In my example I added it to my "minutes" template.
      3. Next, go to a page that uses a template with the field you added above. In my case, "MINUTES"
      4. Enable the checkbox to exclude children, leave it unchecked to include children.
      For example, in my MINUTES page I enabled the checkbox and now when /sitemap.xml is loaded the children for the MINUTES do not appear in the file.

       
      A SIMPLE CONDITIONAL TO CHECK THE "sitemap_exclude_children" VALUE
      This was a pretty easy modification to an existing script, adding only one line. I just figure there may be others out there using this script with the same needs.
      I simply inserted the if condition as the first line in the function:
      function renderSitemapChildren(Page $page) { if($page->sitemap_exclude_children) return ""; ... ... ...  
      THE FULL SCRIPT WITH MODIFICATION
      <?php /** * ProcessWire Template to power a sitemap.xml * * 1. Copy this file to /site/templates/sitemap-xml.php * 2. Add the new template from the admin. * Under the "URLs" section, set it to NOT use trailing slashes. * 3. Create a new page at the root level, use your sitemap-xml template * and name the page "sitemap.xml". * * Note: hidden pages (and their children) are excluded from the sitemap. * If you have hidden pages that you want to be included, you can do so * by specifying the ID or path to them in an array sent to the * renderSiteMapXML() method at the bottom of this file. For instance: * * echo renderSiteMapXML(array('/hidden/page/', '/another/hidden/page/')); * * patch to prevent pages from including children in the sitemap when a field is checked / johnwarrenllc.com * 1. create a checkbox field named sitemap_exclude_children * 2. add the field to the parent template(s) you plan to use * 3. when a new page is create with this template, checking the field will prevent its children from being included in the sitemap.xml output */ function renderSitemapPage(Page $page) { return "\n<url>" . "\n\t<loc>" . $page->httpUrl . "</loc>" . "\n\t<lastmod>" . date("Y-m-d", $page->modified) . "</lastmod>" . "\n</url>"; } function renderSitemapChildren(Page $page) { if($page->sitemap_exclude_children) return ""; /* Aded to exclude CHILDREN if field is checked */ $out = ''; $newParents = new PageArray(); $children = $page->children; foreach($children as $child) { $out .= renderSitemapPage($child); if($child->numChildren) $newParents->add($child); else wire('pages')->uncache($child); } foreach($newParents as $newParent) { $out .= renderSitemapChildren($newParent); wire('pages')->uncache($newParent); } return $out; } function renderSitemapXML(array $paths = array()) { $out = '<?xml version="1.0" encoding="UTF-8"?>' . "\n" . '<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">'; array_unshift($paths, '/'); // prepend homepage foreach($paths as $path) { $page = wire('pages')->get($path); if(!$page->id) continue; $out .= renderSitemapPage($page); if($page->numChildren) { $out .= renderSitemapChildren($page); } } $out .= "\n</urlset>"; return $out; } header("Content-Type: text/xml"); echo renderSitemapXML(); // Example: echo renderSitemapXML(array('/hidden/page/'));  
      In conclusion, I have used a couple different processwire sitemap generating modules. But for my needs, the above script is fast and easy to setup/modify.
      - Thanks
       
    • By Robin S
      Password Generator
      Adds a password generator to InputfieldPassword.

       
      Usage
      Install the Password Generator module.
      Now any InputfieldPassword has a password generation feature. The settings for the generator are taken automatically from the settings* of the password field.
      *Settings not supported by the generator:
      Complexify: but generated passwords should still satisfy complexify settings in the recommended range. Banned words: but the generated passwords are random strings so actual words are unlikely to occur.  
      https://modules.processwire.com/modules/password-generator/
      https://github.com/Toutouwai/PasswordGenerator