Image library : GD driver, error in assigning resize AUTO property

[ae]

When using the resize method you can assign Image::AUTO so that the driver will work out whether it should use the width or height of the image to base the resize on. The problem is that the logic to determine the base property (width OR height) is not correct.

Example: The source image has a width and height of 800 x 600

$image->resize(740,400,Image::AUTO)->quality(80)->save();

In the GD driver it works out whether to use w or h to base the resize on by::

$properties['master'] = ($width > $height) ? Image::WIDTH : Image::HEIGHT;

However, because in the example above the w is greater then the h it bases the resize on the width. This means the resulting resized image is 740 x 555, where the height is GREATER then the height submitted to the method.

The fix for this is to change the way the driver calculates the base to do the resize. Basically by checking the percentage difference between the w and h:

$properties['master'] = (($width / $properties['width']) > ($height / $properties['height'])) ? Image::WIDTH : Image::HEIGHT;

This returns an image of 533x400 which is correct.

The change is for line 197 of the GD library.

[Geert]

Fixed in r3241. Good catch, thanks!