MrZ MrZ - 4 months ago 58
PHP Question

PHP get color at last pixels of image error

I've made this code to get hex colors of the first pixel and the last pixel of an image.
The code for the first pixel is working, I get the HEX code.
But for the last pixel, I've an error:

PHP Notice: imagecolorat(): 1,1024 is out of bounds in /var/playground/imghex.php on line 55


Here's my code:

$gradientHeight = getimagesize($res["gradient"]);
// get Positions
$im = imagecreatefrompng($res["gradient"]);
$rgb = imagecolorat($im, 0, 0);
$r = ($rgb >> 16) & 0xFF;
$g = ($rgb >> 8) & 0xFF;
$b = $rgb & 0xFF;
// store
$res["Gradient1"] = rgb2hex([$r, $g, $b]);
// get positions
print_r($gradientHeight);
$rgb2 = imagecolorat($im, $gradientHeight[0], $gradientHeight[1]);
$r2 = ($rgb2 >> 16) & 0xFF;
$g2 = ($rgb2 >> 8) & 0xFF;
$b2 = $rgb2 & 0xFF;
// store
$res["Gradient2"] = rgb2hex([$r2, $g2, $b2]);
// print
print_r($res);


What's wrong? I don't see any error

Answer

You see that notice because you are using the size on a 0-based index. If you have size of 1024, you'll have positions from 0 to 1023.

That way, you'll need to subtract 1 from it. Replace

$rgb2 = imagecolorat($im, $gradientHeight[0], $gradientHeight[1]);

with

$rgb2 = imagecolorat($im, $gradientHeight[0] - 1, $gradientHeight[1] - 1);
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