通过php文件裁剪图像

Question

so i have an image that is originally 1696x1696. i want to use a php file to MIME a png file. what i want the php to do is crop the original file and produce a quarter of the image. Later i plan to use $_GET variables to return which quadrant i want, but for testing/debugging, im just aiming to get the top left quadrant.

here's the code:

Header("Content-type:image/png");
$newImg =imagecreatefrompng('test.png'); 

//manually entered half height and width
$img=imagecreatetruecolor(848,848);
//here is where the bugs keep flawing the image
imagecopyresampled($img,$newImg,0,0,0,0,1696,1696,1696,1696);
imagepng($img); 
imagedestroy($img);

this will produce the image (top, left) like it's supposed to, however it adds several smaller resampled images on top of it. no matter how i toy with it, i cant get it right. i've also tried imagecopy() and cant get it right as well. looked up tutorials and i cant seem to find on that helps.

Answer 1

Your code looks fine. The only thing I would change is to use imagecopyresized() instead of imagecopyresampled() in this use case.

Header("Content-type:image/png");
$source = imagecreatefrompng('images/test.png'); 

// manually entered half height and width
$thumb  = imagecreatetruecolor(848,848);

imagecopyresized($thumb, $source, 0, 0, 0, 0, 1696, 1696, 1696, 1696);
imagepng($thumb); 
imagedestroy($thumb);

I am guessing that earlier in your tests, you were overwriting your original image. That would explain the...

however it adds several smaller resampled images on top of it...

...part of your experience. Each time you ran the code, you picked up the previously modified file.