Scale or Resize an image by a percentage

Hi, i am interested by this issue because i have already implemented an similar feature in Automated crop project.

    // The width & height of auto crop area must large than min sizes.
    $this->cropBox['width'] = max($this->cropBox['min_width'], $width * $this->autoCropArea);
    $this->cropBox['height'] = max($this->cropBox['min_height'], $height * $this->autoCropArea);

The autoCropArea parameter are used to "adjust" the final size of cropBox.

IMHO, that can be an simple / powerfull option to add in other Effects in option by example 'Scale & crop' 'Automated Crop' 'Resize'.

Needed this, here is the plugin.

Thanks @Sam152

1. The imagecache_actions version of this effect allows setting height/width percentage separately, whereas this patch is limited at defining a single percentage value for scaling. Do we want a separate effect for the split height/width resize, or shall it be included in the patch here? Opinions welcome.
2. The effect changes the dimensions of the image. As such, it needs to implement ::trasformDimensions.
3. ::getSummary (and theme_hook entry + template) is missing from the effect.
4. Need to add a line describing the effect in README.md
5. The test should extend from \Drupal\image_effects\Tests\ImageEffectsTestBase, which is a WTB test. All the effects in the module extend from it. This will make it easier to convert all tests together later.

As a reference for entering a new effect in a single commit, see http://cgit.drupalcode.org/image_effects/commit/?id=7e79819

At this stage, I don't have capacity to implement the changes requested, given #3 works for my use case.

If anyone would like to push this forward, please feel free to implement changes in #5.

@mondrake, Have you already seen automated_crop ? I think in this module we have an effect similar to what you describe. Eg : possibility to enter height/width and/or percents. If that can be usefull here I can purpose a patch to delete it to automated_crop and based this effects onto image_effect (why not).

@woprrr thanks, I had a quick glance - it looks like the automated_crop effect has a very specific use case and it introduces a specific service to manage the crop. That said, if it can be 'extracted' and be able to work in isolation (i.e. without needing that module as a dependency), and fits in the concept here (i.e. just resizing/scaling the source image to a percentage), then as you say, why not?

If you just consider moving the automated_crop effect to the module here, then fine as well, but that would be a separate issue IMHO.

If you want to take it on, please mind the naming conventions and the testing approach described in #5. It can be a bit painful, but please consider we are trying to establish a common pattern for introducing any new effect to this module.

Taking it on

Here's a new patch, addressing points in #5.

Committed.