Image resizing quality

[Vikestart]

What is up with the quality of images when they are resized? Is there anything that can be done to increase the quality?

Compare the two:

Original:

 

Resized (barely smaller):

 

The quality loss is enormeous, especially in dark areas of the image.

[Robin S]

1 hour ago, Vikestart said:

What is up with the quality of images when they are resized?

What's up is that the size() method accepts a 'quality' setting in its $options array: https://processwire.com/api/ref/pageimage/size/

And you can define the default quality setting used for the image sizer in /site/config.php via $config->imageSizerOptions: https://processwire.com/api/ref/config/

[Vikestart]

18 minutes ago, Robin S said:

What's up is that the size() method accepts a 'quality' setting in its $options array: https://processwire.com/api/ref/pageimage/size/

And you can define the default quality setting used for the image sizer in /site/config.php via $config->imageSizerOptions: https://processwire.com/api/ref/config/

Oooh, I didn't even know about that config.php file and that list of settings you linked to is certainly useful.

Still getting to know Processwire. I'll just dive in and see where this gets me  Thanks!

[Christophe]

By default PHP's bundled GD 2 library is used.

If you're using a recent ProcessWire 3 version, ImageMagick is also supported (if you can have it installed on your server of course).

Perhaps you could have better results.

https://processwire.com/blog/posts/processwire-3.0.10-expands-image-resize-options/

NB: in /wire/config.php you can also see some settings, copy them to /site/config.php and modify them...

Edited April 5, 2017 by Christophe

[horst]

..., and you should enable the IMagick Imagesizer Engine if your server supports it! (under PW 3)

..., and additionally to the quality-value, you can try out differend sharpening values (none, soft, medium, strong)

[Vikestart]

Setting the defaultGamma option to 0.5 instead of the default 2.0 seems to have fixed the image quality.

$config->imageSizerOptions = array('upscaling' => true, 'cropping' => true, 'quality' => 100, 'sharpening' => 'none', 'defaultGamma' => 0.5);

Thanks for the help everyone! 

[Peter Knight]

On 4/6/2017 at 12:43 AM, Vikestart said:

Setting the defaultGamma option to 0.5 instead of the default 2.0 seems to have fixed the image quality.

$config->imageSizerOptions = array('upscaling' => true, 'cropping' => true, 'quality' => 100, 'sharpening' => 'none', 'defaultGamma' => 0.5);

Thanks for the help everyone! 

@Vikestart

Did you paste this from your config in /wire/ to your config file in /site/ ?

[Peter Knight]

Confirming this worked for me too. ?

[horst]

Have you also tried -1 ?