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Re: Help with PHP BD imaging functionality

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On 8/7/2013 7:53 PM, Ed Jay wrote:
> I'm trying to highlight a portion of a grayscale image, with the
> highlighting color applied to pixels within a range of level only. I'm not
> getting the result I seek.
>
> While the grayscale values within the range possibly yield the highlight
> color, the entire image is masked with the color from the last
> imagecolorallocate.
>
> My code follows, and the 'Process of interest' is the offending culprit.
>
> How do I highlight the value-region of interest with the background of my
> choosing?
>
> $source_image = $_GET['source'];
> $threshold = $_GET['threshold'];
> $range = $_GET['range'];
>
> $starting_img = imagecreatefromjpeg($source_image);
> $img_data = getimagesize($source_image);
> $width = $img_data[0];
> $height = $img_data[1];
> $final = imagecreatetruecolor($img_data[0],$img_data[1]);	
>
> $gray_threshold = 1*$threshold;
> $gray_range = 1*$range;
> $gray_top = ($gray_threshold + $gray_range);
> if ($gray_top > 255) {$gray_top = 255;}
> $highlight_color = imagecolorallocate($final,0,0,255);
>
> //Process of interest:
>
> 	for($x=0; $x<$width; $x++){
>      	for($y=0; $y<$height; $y++){
>
> 	$gray =(imagecolorat($final,$x,$y) >> 16) & 0xFF;
> 	if (($gray > $gray_threshold) && ($gray < $gray_top)) {$gray =
> $highlight_color;}
> 	$gray2 = imagecolorallocate($final,$gray,$gray,$gray);
> 	imagesetpixel($final, $x,$y,$gray2);
>
> 	}
> 	}
>
> header('Content-Type: image/jpeg');
> imagejpeg($final);
> imagedestroy($starting_img);
> imagedestroy($final);
>
> Thanks in advance,
>

Hi, Ed,

I think I understand what you're trying to do, but haven't actually run 
the code (I don't happen to have any gray scale jpegs handy right now).

I see you create the $starting_image.  However, I don't see where you 
use it again.  You don't copy the image into $final, so after

$final = imagecreatetruecolor($img_data[0],$img_data[1]);	

$final is black.

I also don't see

Perhaps

$gray =(imagecolorat($final,$x,$y) >> 16) & 0xFF;

should be using $starting_image instead of $final?

Alternatively, why are you creating $final?  Why not operate on 
$starting_image directly?

-- 
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
==================

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Thread

Help with PHP BD imaging functionality Ed Jay <edMbj@aes-intl.com> - 2013-08-07 16:53 -0700
  Re: Help with PHP BD imaging functionality The Natural Philosopher <tnp@invalid.invalid> - 2013-08-08 08:58 +0100
    Re: Help with PHP BD imaging functionality Ed Jay <edMbj@aes-intl.com> - 2013-08-08 05:01 -0700
      Re: Help with PHP BD imaging functionality The Natural Philosopher <tnp@invalid.invalid> - 2013-08-08 14:12 +0100
        Re: Help with PHP BD imaging functionality Christoph Michael Becker <cmbecker69@arcor.de> - 2013-08-09 01:13 +0200
  Re: Help with PHP BD imaging functionality Jerry Stuckle <jstucklex@attglobal.net> - 2013-08-08 08:55 -0400

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