PHP: imagecopymergegray

User Contributed Notes
imagecopymergegray

switch251 at netcourrier dot com
15-Apr-2004 09:18


In addition to code_couturier too: his code will produce blue pictures, because the value he uses to set the pixel color (the code is incomplete: I first thought it should be $gray) is between 0 and 255, which corresponds to blue levels.



To convert the picture to grayscale, use the following code:



<?php

    // replace with your files

    $originalFileName    = "colorPicture.jpg";

    $destinationFileName = "bwPicture.jpg";

    

    // create a copy of the original image

    // works with jpg images

    // fell free to adapt to other formats ;)

    $fullPath = explode(".",$originalFileName);

    $lastIndex = sizeof($fullPath) - 1;

    $extension = $fullPath[$lastIndex];

    if (preg_match("/jpg|jpeg|JPG|JPEG/", $extension)){

        $sourceImage = imagecreatefromjpeg($originalFileName);

    }



    // get image dimensions

    $img_width  = imageSX($sourceImage);

    $img_height = imageSY($sourceImage);



    // convert to grayscale

    // note: this will NOT affect your original image, unless

    // originalFileName and destinationFileName are the same

    for ($y = 0; $y <$img_height; $y++) { 

        for ($x = 0; $x <$img_width; $x++) { 

            $rgb = imagecolorat($sourceImage, $x, $y);

            $red   = ($rgb >> 16) & 0xFF;

            $green = ($rgb >> 8)  & 0xFF;

            $blue  = $rgb & 0xFF;



            $gray = round(.299*$red + .587*$green + .114*$blue);

            

            // shift gray level to the left

            $grayR = $gray << 16;   // R: red

            $grayG = $gray << 8;    // G: green

            $grayB = $gray;         // B: blue

            

            // OR operation to compute gray value

            $grayColor = $grayR | $grayG | $grayB;



            // set the pixel color

            imagesetpixel ($sourceImage, $x, $y, $grayColor);

            imagecolorallocate ($sourceImage, $gray, $gray, $gray);

        }

    }



    // copy pixel values to new file buffer

    $destinationImage = ImageCreateTrueColor($img_width, $img_height);

    imagecopy($destinationImage, $sourceImage, 0, 0, 0, 0, $img_width, $img_height);



    // create file on disk

    imagejpeg($destinationImage, $destinationFileName);

    

    // destroy temp image buffers

    imagedestroy($destinationImage);    

    imagedestroy($sourceImage);

?>



Copy-paste, replace the file names on the top and there you go (picture files must be in same folder as this script. If not, you will have to do your own file management).

annonymous at example dot com
15-Feb-2004 06:25


in addition to code_couturier - try this formula to calculate gray-value (luminance) in his "more exact" way:



$gray = round(.299*$red + .587*$green + .114*$blue);

code_couturier at graffiti dot net
18-Oct-2003 02:08


# very fast way to generate a grayscal-

# image from a true color image



#...



# --- quick grayscale image

for ($y = 0; $y <$img_height; $y++) { 

 for ($x = 0; $x <$img_width; $x++) { 



 # here we extract the green from 

 # the pixel at x,y , to use it as gray value

 $gray = (ImageColorAt($image, $x, $y) >> 8) & 0xFF;



 # a more exact way would be this:

 # $rgb = ImageColorAt($image, $x, $y);

 # $red = ($rgb >> 16) & 0xFF;

 # $green = (trgb >> 8) & 0xFF;

 # $blue = $rgb & 0xFF;

 # $gray = (int)(($red+$green+$blue)/4); 



 # and here we set the new pixel/color

  imagesetpixel ($image, $x, $y, 

  ImageColorAllocate ($image, $gray,$gray,$gray));

 }

}

 

# ...

mail at laeubi dot de
09-Oct-2003 02:45


This function don't work properly for me on trucolerimages (have not tried yet for other types) it jsut produce a part-grayscale image, and some color get mesed up.

I found a workaround here:

http://www.phpbuilder.com/columns/cash20030526.php3?page=2



[quote]

Advanced Image Editing Under the GD Library

Colorizing

Colorizing images is fairly easy to do. The easiest way to colorize an image is fairly simple to grasp. Create an image of the same dimensions and fill that image with the color you want to change it to. This new image is then placed on top of the older image, giving it a colorized look.



<?php 

function imagecolorize(&$im,&$col,$pct) { 

    // Get the image's width 

    $im_w = imagesx($im);  

    // Get the image's height 

    $im_h = imagesy($im);  

    // Set a pixel with the color, so we can get it easily 

    $setpixel = imagesetpixel($im,$im_w,0,$col);  

    // Get the color 

    $index = imagecolorat($im,$im_w,0);  

    // Find the color in the index 

    $rgb = imagecolorsforindex($im,$index);  

    // Get the red value 

    $r = $rgb["red"]; 

    // Get the green value 

    $g = $rgb["green"];  

    // Get the blue value 

    $b = $rgb["blue"];  

    // Create the layover 

    $layover = imagecreate($im_w,$im_h);  

    // Allocate the color on this image 

    $color = imagecolorallocate($layover,$r,$g,$b);  

    // Fill the image with the new color (this really isn't needed) 

    $fill = imagefill($layover,0,0,$color);  

    // Merge the layover on top of the older image 

    $merge = imagecopymerge($im,$layover,0,0,0,0,$im_w,$im_h,$pct); 

    imagedestroy($layover); // Destroy the layover 

} 

?> 



If we use a blue layover RGB(0,0,255), we get this result:

[/quote]



if you use black or gray, its not perfekt, but better than nothing ;)

imagecopymergegray

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