Milburn

I created some stereographic pairs yesterday and used some online software to create an anaglyph for viewers with red and cyan glasses. Creating anaglyphs is in fact a really easy task. All that has to be done is to separate the red layer from the left image and the green and blue layers from the right image. Finally the three layers are combined to create a colour anaglyph. Simple.

Having a little experience with PHP, I decided to create a simple script to create anaglyphs. First I needed to plan out how the script was going to work. The GD library has no native image filters except in PHP5. My plan works like so.

Find the size of the image
For every x coordinate
  For every y coordinate
    Get the red value of the left pixel
    Get the green value of the right pixel
    Get the blue value of the right pixel
    Set the result pixel to red + green + blue
Output image

In PHP this results in:

// The file for the left eye
$left = 'left.jpg';
// The file for the right eye
$right = 'right.jpg';
// Get the dimensions
list($width, $height) = getimagesize($left);
// Define our source images
$src_right = imagecreatefromjpeg($right);
$src_left = imagecreatefromjpeg($left);
// Create the canvas
$bwimage= imagecreatetruecolor($width, $height);
//Reads the origonal colors pixel by pixel
for ($y=0;$y<$height;$y++){
for ($x=0;$x<$width;$x++){
$rgb_left = imagecolorat($src_left,$x,$y);
$r = ($rgb_left >> 16) & 0xFF;
$rgb_right = imagecolorat($src_right,$x,$y);
$g = ($rgb_right >> 8) & 0xFF;
$b = $rgb_right & 0xFF;
//This is where we create the color which is a mix of the red, green and blue channels
$color = imagecolorallocate($bwimage,$r,$g,$b);
imagesetpixel($bwimage,$x,$y,$color);
}
}
// This sets it to a .jpg, but you can change this to png or gif if that is what you are working with
header('Content-type: image/jpeg');
imagejpeg($bwimage);
?>

I didn’t think this would work at first because it seems too simple. My tests revealed the images I was outputing were the same as other programmes so it was working. Having said that since I cant find any red and cyan glasses I can’t really test it properly! Can anyone else verify the images below?

Update: If you want to create your own anaglyphs why not use my free anaglyph creator.