imagesetpixel() Troubles

[Taorluath]

I'm trying to make a PHP script that increases the blue value of each pixel in an image by 1.

It's important that the script goes pixel by pixel.

For some reason, however, it outputs an image that is one solid color; a brownish red block.

Why isn't this script only slightly increasing the values?? ??? ???

 

 

 

<?php
$img = imagecreatefromgif('logo.gif');

// get height and width
$h=imagesy($img);
$w=imagesx($img);

//display image
echo "<img src='out.gif' />";

//cycle through every pixel and add 1 to the blue value of the pixel's rgb value
$y=1;
while($y < $h) {
$x=1;
while($x < $w) {

$rgb = imagecolorat($img, $x, $y);
$red = ($rgb >> 16) & 0xFF;
$green = ($rgb >>  & 0xFF;
$blue = $rgb & 0xFF;
$blue++;

//define the new color and assign it to the pixel
//this is where things go wrong
$color = imagecolorallocate($img, $red, $green, $blue);
imagesetpixel($img, $x, $y, $color);
$x++;
}
$y++;
}

echo imagegif($img, 'out.gif');
?>

 

I know the problem is in these two lines by the way.

$color = imagecolorallocate($img, $red, $green, $blue);
imagesetpixel($img, $x, $y, $color);

[ratcateme]

i added this after $blue++;

echo "{$x},{$y}	RGB:	{$rgb}|RED:	{$red}|Greeen:	{$green}|Blue:	{$blue}\n\n";

it shows that the problem is not in setting the color but getting the old color however i don't no what causes this problem

 

Scott.

[Barand]

Allocating a new color in the pallette for every pixel doesn't look like a good idea.

 

You could try attacking the pallette rather than every single pixel. Much quicker.

 

<?php

$img = imagecreatefromgif('baa.gif');


//cycle through pallette add 1 to the blue value of color's rgb value
$t = imagecolorstotal($img);
for ($i=0; $i<$t; $i++)
{
        $cols = imagecolorsforindex($img, $i);
        $blue = $cols['blue'] < 255 ? $cols['blue']+1 : $cols['blue'] ;
        imagecolorset($img, $i, $cols['red'], $cols['green'], $blue);
}

imagegif($img);
?>