PHP GD image merge changing my image to black - php

Question

I have a very frustrating situation. I am using PHP GD for the first time, and it's been a bit of a rollercoaster relationship. Basically, I am trying to merge 2 images, a square one (with a height/width of x) onto a rectangle (with a width of x and a height of y).
The square needs to be centered vertically. But this isn't the issue - I've managed to position it correctly.
Whats happening is, my rectangle is white. My square has a white background, so when the images are merged, it should just look like my asset on a white rectangluar background.
When I merge the image though, GD is for some reason changing my background white rectangle to black - so you can see the white square in the middle, with black "bars" on top and bottom. Can anyone help?
Code is:
//create copy of original image to correct size
imagecopyresized($dst_image, $src_image, 0,0,0,0,$x_width,$x_height,$orig_img_x_width,$orig_img_x_height);
imagejpeg($dst_image, "resized_copy.jpg", 100);
$img = imagecreatetruecolor(1333, 2000);
$white = imagecolorallocate($img, 255, 255, 255);
imagefill ( $img, 0, 0, $white );
imagefilledrectangle($img,0,0,1333,2000, $white);
imagejpeg($img, "rectangle.jpg", 100);
//merge images
$dest2 = imagecreatefromjpeg("rectangle.jpg");
$src2 = imagecreatefromjpeg('resized_copy.jpg');
imagecopymerge($dest2, $src2, 0, 0, 0, -333.5, $x_width, $x_height, 100);
imagejpeg($dest2, "final_image.jpg", 100);
I've tried using imagecopy instead of imagecopymerge, but I get the same result. I'm sure there is a simple explanation, but I cant seem to find it trawling through the php manual.

Answer 1

I've read your question a few times but I'm not convinced I understand exactly what you are trying to achieve so I've made a few assumptions in producing the below code.
For the sake of simplicity I've created a 'square.jpg' test image file like so:
(Note that I've used small image sizes here so I can show them inline.)
// read in the square test image.
$square = imagecreatefromjpeg('square.jpg');
$square_x = imagesx($square); // 100px
$square_y = imagesy($square); // 100px
// create the rectangular image to merge with.
$rectangle = imagecreatetruecolor(100, 200);
$rectangle_x = imagesx($rectangle); // 100px
$rectangle_y = imagesy($rectangle); // 200px
// note that this isn't white, but rather a lovely shade of blue to better
// show the image on the white SO background!
$white = imagecolorallocate($rectangle, 128, 128, 255);
imagefill($rectangle, 0, 0, $white);
// merge the images.
imagecopymerge(
$rectangle,
$square,
0,
($rectangle_y / 2) - ($square_y / 2), // to vertically centre the square.
0,
0,
$square_x,
$square_y,
75 // Just to show the merge clearly; change back to 100 for your usage.
);
imagejpeg($rectangle, 'final_image.jpg', 100);
imagedestroy($rectangle);
imagedestroy($square);
This gives me the following image in final_image.jpg: