I’m creating an uploader that can upload jpg, giff and png images. Then converts them all too transparent PNG’s and then crops the image based on crop parameters send from client side. The crop can even supply negative axis coordinates, meaning the image is being cropped beyond image dimensions.
To ensure all supported formats can have transparency I first recreate the image into a transparent png, and this is working well.
//GET WIDTH AND HIEGHT OF UPLOADED JPG
list($imageWidth,$imageHeight)= getimagesize($originalDirectory.$file_name);
$image = imagecreatefromjpeg($originalDirectory.$file_name);
//CREATE NEW IMAGE BASED ON WIDTH AND HEIGHT OF SROUCE IMAGE
$bg = imagecreatetruecolor($imageWidth, $imageHeight);
//TRANSPARENCY SETTINGS FOR BOTH DESTINATION AND SOURCE IMAGES
$transparent2 = imagecolorallocatealpha($bg, 0, 0, 0, 127);
$transparent = imagecolorallocatealpha($image, 0,128,255,50); //ONLY TO ENSURE TRANSPARENCY IS WORKING
//SAVE TRANSPARENCY AMD FILL DESTINATION IMAGE
imagealphablending( $bg, false );
imagesavealpha($bg, true);
imagefill($bg, 0, 0, $transparent2);
//SAVE TRANSPARENCY AMD FILL SOURCE IMAGE
imagealphablending( $image, false );
imagesavealpha($image, true);
imagefill($image, 0, 0, $transparent); //ONLY TO ENSURE TRANSPARENCY IS WORKING
//CREATE AND SAVE AS PNG FILE WITH TRANSPARENCY
imagecopy($bg, $image, 0, 0, 0, 0, $imageWidth,$imageHeight);
header('Content-type: image/png');
imagepng($bg, $originalDirectory.$jpgFile);
imagedestroy($bg);
After the new png is created I use it to then only crop the image according to the parameters passed through from the client side scripting.
//GET NEWLY CREATED PNG
$src = imagecreatefrompng($originalSRC);
// NOT SURE IF NECESSARY BUT HAS NO EFFECT ON FINAL RESULT REGGARDLESS OF ANY SETTINGS DONE
imagealphablending( $image, false );
imagesavealpha($image, true);
//DEFINE DESTINATION CROPPED FILE
$thumbHighFilename = $thumbHighDirectory.'test.png';
//CREATE NEW IMAGE BASED ON FINAL CROP SIZE
$tmp = imagecreatetruecolor($cropWidth, $cropHeight);
//ENSURE DESTINATION HAS TRANSPARENT BACKGROUND
$transparent2 = imagecolorallocatealpha($tmp, 0, 0, 0, 127);
imagealphablending( $tmp, false );
imagesavealpha($tmp, true);
imagefill($tmp, 0, 0, $transparent2);
/* -------------------------------------------------
PROBLEM HERE
When I try to merge the two with the crop paramaters
send from client side. All transparencies work, except
where crop X and Y axis exceeds source image paramaters.
Currently 50px offset on destination image is to verify
transparency works.
The source coordinates are based on image not crop area.
Tried with both imagecopyresized & imagecopyresampled
-------------------------------------------------*/
imagecopyresized($tmp, $src, -50,-50, $xAxis,$yAxis,$cropWidth, $cropHeight, $pW, $pH);
//SAVE FINAL IMAGE
header('Content-type: image/png');
imagepng($tmp, $thumbHighFilename);
imagedestroy($tmp);
This is where the source and destination images still has there transparency; however the negative coordinates creates a black background around the source image. How can I get that to be transparent?
While I found a lot about transparencies, nothing has been a proper solution. For example imagefill afterwards will not work as source could use 100% black around the edges and will make that also transparent then, which it shouldn’t.