GD Library, it is possible?

[lopes_andre]

Hi,

 

I need to do something like this, but with GD, it is possible?

 

http://eclecticdjs.com/mike/tutorials/php/imagemagick/examples_01/blackthreshold.php

 

Given a colour, transform that colour to black.

 

It is possible with GD?

 

Best Regards,

[lemmin]

Yeah, you can do that. You could iterate through each pixel with imagecolorat().

 

http://us.php.net/manual/en/function.imagecolorat.php

[lopes_andre]

Thanks for the reply,

 

I'am testing this code, but it is not working...

 

<?php
   $img = imagecreatefromjpeg("image2.jpg");
  
   $w = imagesx($img);
   $h = imagesy($img);
  
   for($y=0;$y<$h;$y++) {
      for($x=0;$x<$w;$x++) {
         $rgb = imagecolorat($img, $x, $y);        
         imagecolorset($img, $rgb, 0, 0, 255);
      }
   }
?>

 

Any clue?

 

Best Regards,

[Alex]

That code will loop through every color and change that color to blue. Making the entire image blue. Try something like:

 

$img = imagecreatefromjpeg("image2.jpg");
$rgb = imagecolorat($img, $x, $y); // replace $x and $y here to be the point you want..     
imagecolorset($img, $rgb, 0, 0, 255);

 

You're also not outputting the new image to see the changes. Add this to the end of the script:

 

header('Content-type: image/jpeg');
imagejpeg($img);

 

imagejpeg

[lopes_andre]

Thanks for the reply,

 

I'am testing with both codes, but the codes don't do anything...

 

<?php
   $img = imagecreatefromjpeg("image2.jpg");
  
   $w = imagesx($img);
   $h = imagesy($img);
  
   for($y=0;$y<$h;$y++) {
      for($x=0;$x<$w;$x++) {
         $rgb = imagecolorat($img, $x, $y);        
         imagecolorset($img, $rgb, 0, 0, 0);
      }
   }
   imagejpeg($img, 'simpleimg.jpg');
?>

 

Any clue?

 

Best Regards,

[lopes_andre]

Any clue on what might be wrong on the code?

 

Best Regards,

 

[Alex]

Did you change the $x and $y to the x and y of the pixel containing the color that you want to replace?

[lopes_andre]

Did you change the $x and $y to the x and y of the pixel containing the color that you want to replace?

 

Yes, I have changed, but didn't see any change, so I put the code in the FOR Loops, but no changes in the image. Some clue on what could be wrong?

 

Best Regards,

 

[Alex]

It should work as long as you're inputting the correct information. The script should look something like this:

 

$img = imagecreatefromjpeg("image2.jpg");
$rgb = imagecolorat($img, $x, $y); // replace $x and $y here to be the point you want..     
imagecolorset($img, $rgb, 0, 0, 255);
header('Content-type: image/jpeg');
imagejpeg($img);

 

That would take image2.jpg and take whatever color is at point ($x, $y) and replace it throughout the whole image with blue, and then display it in the browser.

[lopes_andre]

Hi,

 

Thanks for the reply.

 

I'am seeing the result with the above code, so I have tried with:

 

<?php
   $img = imagecreatefromjpeg("image2.jpg");
  
   $w = imagesx($img);
   $h = imagesy($img);
  
   for($y=0;$y<$h;$y++) {
      for($x=0;$x<$w;$x++) {
         $rgb = imagecolorat($img, $x, $y);        
         imagecolorset($img, $rgb, 0, 0, 0);
      }
   }
   imagejpeg($img, 'simpleimg.jpg');
?>

 

Unfortunately it is not working.

 

Some clue?

[Alex]

$img = imagecreatefromjpeg("image2.jpg");
$rgb = imagecolorat($img, $x, $y); // replace $x and $y here to be the point you want..     
imagecolorset($img, $rgb, 0, 0, 255);
header('Content-type: image/jpeg');
imagejpeg($img, 'simpleimg.jpg');