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18 years ago
While replying to a post in a support forum I noticed something odd about imagecopy(). The first snippet (should) create an image object, allocate a colour resource within that image, fill the background with the allocated colour and then copy another, cropped to fit, image onto it.

<?php
    // create a new image resource
    $temp = imagecreatetruecolor( $width, $height );
    $white = imagecolorallocate( $temp, 255, 255, 255 );

    //fill the background with white
    imagefill( $temp, 0, 0, $white );

    //copy the image into new a resource
    imagecopy($temp, $this->Image, 0, 0, $crop_top, $crop_left, $width, $height);
?>

But this produces a black background. I noticed taking away the imagefill() call yields the same results. The solution was to call imagefill() after the imagecopy(). Thinking linearly I would have guessed this to cover the previously copied image in white but it doesn't. I guess GD uses a layer system? Is this correct?

<?php
    // create a new image resource
    $temp = imagecreatetruecolor( $width, $height );
    $white = imagecolorallocate( $temp, 255, 255, 255 );

    // copy image into new resource
    imagecopy( $temp, $this->Image, 0, 0, $crop_top, $crop_left, $width, $height );
        
    //fill the background with white (not sure why it has to be in this order)
    imagefill( $temp, 0, 0, $white );
?>

I am using php 5.1.4 with the bundled GD (2.0.28)
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