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Digg  imagecolorsforindex
Get the colors for an index
(PHP 4, PHP 5)
Example 993. imagecolorsforindex() example<?phpThe above example will output something similar to: ArrayCode Examples / Notes » imagecolorsforindexadspeed.com
To correct m4551 at abasoft dot it example: ImageTrueColorToPalette($im,1,$t); might give less colors than $t, so the for loop should call "$i<ImageColorsTotal($im)" instead of "$i<$t" just to be sure, or you'll get the warning: Color index [0-9] out of range admin
this is a sepia filter using microsoft's definition <?php function imagesepia( $img ) { $total = imagecolorstotal( $img ); for ( $i = 0; $i < $total; $i++ ) { $index = imagecolorsforindex( $img, $i ); $red = ( $index["red"] * 0.393 + $index["green"] * 0.769 + $index["blue"] * 0.189 ) / 1.351; $green = ( $index["red"] * 0.349 + $index["green"] * 0.686 + $index["blue"] * 0.168 ) / 1.203; $blue = ( $index["red"] * 0.272 + $index["green"] * 0.534 + $index["blue"] * 0.131 ) / 2.140; imagecolorset( $img, $i, $red, $green, $blue ); } } ?> strozek a deas harvard edu
Regarding m4551's method of conversion -- the actual CCIR-approved RGB-to-grayscale conversion is as follows: grayscale component = 0.2125*R + 0.7154*G + 0.0721*B (cf. CCIR Recommendation 709 for modern monitors) slepichev
If you would like to change the intensity or lightness level of a specific color, you will need to convert the color format from RGB to HSL. following function convert RGB array(red,green,blue) to HSL array(hue, saturation, lightness) <?php /** * Convert RGB colors array into HSL array * * @param array $ RGB colors set * @return array HSL set */ function rgb2hsl($rgb){ $clrR = ($rgb[0] / 255); $clrG = ($rgb[1] / 255); $clrB = ($rgb[2] / 255); $clrMin = min($clrR, $clrG, $clrB); $clrMax = max($clrR, $clrG, $clrB); $deltaMax = $clrMax - $clrMin; $L = ($clrMax + $clrMin) / 2; if (0 == $deltaMax){ $H = 0; $S = 0; } else{ if (0.5 > $L){ $S = $deltaMax / ($clrMax + $clrMin); } else{ $S = $deltaMax / (2 - $clrMax - $clrMin); } $deltaR = ((($clrMax - $clrR) / 6) + ($deltaMax / 2)) / $deltaMax; $deltaG = ((($clrMax - $clrG) / 6) + ($deltaMax / 2)) / $deltaMax; $deltaB = ((($clrMax - $clrB) / 6) + ($deltaMax / 2)) / $deltaMax; if ($clrR == $clrMax){ $H = $deltaB - $deltaG; } else if ($clrG == $clrMax){ $H = (1 / 3) + $deltaR - $deltaB; } else if ($clrB == $clrMax){ $H = (2 / 3) + $deltaG - $deltaR; } if (0 > $H) $H += 1; if (1 < $H) $H -= 1; } return array($H, $S, $L); } ?> m4551
here's a function to greyscale an image even from a truecolor source (jpeg or png). slightly poor quality, but very fast... function imagegreyscale(&$img, $dither=1) { if (!($t = imagecolorstotal($img))) { $t = 256; imagetruecolortopalette($img, $dither, $t); } for ($c = 0; $c < $t; $c++) { $col = imagecolorsforindex($img, $c); $min = min($col['red'],$col['green'],$col['blue']); $max = max($col['red'],$col['green'],$col['blue']); $i = ($max+$min)/2; imagecolorset($img, $c, $i, $i, $i); } } tim
Here's a better grayscale, sepia, and general tinting function. This function is better because: 1) Works with true color images (the other sepia code didn't). 2) Provides a more gooder grayscale conversion (yes, I said "more gooder"). The other grayscale code used imagetruecolortopalette, which just doesn't work well for grayscale conversion. 3) The other sepia code was really colorful, a little too much for my taste. This function allows you to optionally set the tinting of the grayscale to anything you wish. 4) Single function for grayscale, sepia, and any other tinting you can dream up. Here's some examples: imagegrayscaletint ($img); // Grayscale, no tinting imagegrayscaletint ($img,304,242,209); // What I use for sepia imagegrayscaletint ($img,0,0,255); // A berry blue image The RGB values for tinting are normally from 0 to 255. But, you can use values larger than 255 to lighten and "burn" the image. The sepia example above does this a little, the below example provides a better example of lightening the image and burning the light areas out a little: imagegrayscaletint ($img,400,400,400); // Lighten image imagegrayscaletint ($img,127,127,127); // Darken image <? function imagegrayscaletint (&$img, $tint_r = 255, $tint_g = 255, $tint_b = 255) { $width = imagesx($img); $height = imagesy($img); $dest = imagecreate ($width, $height); for ($i=0; $i<256; $i++) imagecolorallocate ($dest, $i, $i, $i); imagecopyresized ($dest, $img, 0, 0, 0, 0, $width, $height, $width, $height); for ($i = 0; $i < 256; $i++) imagecolorset ($dest, $i, min($i * abs($tint_r) / 255, 255), min($i * abs($tint_g) / 255, 255), min($i * abs($tint_b) / 255, 255)); $img = imagecreate ($width, $height); imagecopy ($img, $dest, 0, 0, 0, 0, $width, $height); imagedestroy ($dest); } ?> |
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