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Enhance GD::greyscale to allow darker or lighter results #5332

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Merged
sminnee merged 1 commit into from
Apr 21, 2016
Merged

Enhance GD::greyscale to allow darker or lighter results #5332

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27 changes: 16 additions & 11 deletions filesystem/GD.php
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Original file line number Diff line number Diff line change
Expand Up @@ -486,14 +486,16 @@ public function paddedResize($width, $height, $backgroundColor = "FFFFFF") {
}

/**
* Make the image greyscale
* $rv = red value, defaults to 38
* $gv = green value, defaults to 36
* $bv = blue value, defaults to 26
* Based (more or less entirely, with changes for readability) on code from
* http://www.teckis.com/scriptix/thumbnails/teck.html
* Make the image greyscale.
* Default color weights are based on standard BT.601 (those used in PAL, NTSC and many software packages, also see
* https://en.wikipedia.org/wiki/Grayscale#Luma_coding_in_video_systems )
*
* $R = red weight, defaults to 299
* $G = green weight, defaults to 587
* $B = blue weight, defaults to 114
* $brightness = brightness in percentage, defaults to 100
*/
public function greyscale($rv=38, $gv=36, $bv=26) {
public function greyscale($R=299, $G=587, $B=114, $brightness=100) {
$width = $this->width;
$height = $this->height;
$newGD = imagecreatetruecolor($this->width, $this->height);
Expand All @@ -502,15 +504,18 @@ public function greyscale($rv=38, $gv=36, $bv=26) {
imagealphablending($newGD, false);
imagesavealpha($newGD, true);

$rt = $rv + $bv + $gv;
$rr = ($rv == 0) ? 0 : 1/($rt/$rv);
$br = ($bv == 0) ? 0 : 1/($rt/$bv);
$gr = ($gv == 0) ? 0 : 1/($rt/$gv);
$rt = $R + $G + $B;
// if $rt is 0, bad parameters are provided, so result will be a black image
$rr = $rt ? $R/$rt : 0;
$gr = $rt ? $G/$rt : 0;
$br = $rt ? $B/$rt : 0;
// iterate over all pixels and make them grey
for($dy = 0; $dy < $height; $dy++) {
for($dx = 0; $dx < $width; $dx++) {
$pxrgb = imagecolorat($this->gd, $dx, $dy);
$heightgb = ImageColorsforIndex($this->gd, $pxrgb);
$newcol = ($rr*$heightgb['red']) + ($br*$heightgb['blue']) + ($gr*$heightgb['green']);
$newcol = min(255, $newcol*$brightness/100);
$setcol = ImageColorAllocateAlpha($newGD, $newcol, $newcol, $newcol, $heightgb['alpha']);
imagesetpixel($newGD, $dx, $dy, $setcol);
}
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4 changes: 2 additions & 2 deletions tests/filesystem/GDTest.php
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Expand Up @@ -91,8 +91,8 @@ protected function assertGreyscale($samples, $alphaBits = 0, $tolerance = 0) {
}

// check various sample points
$this->assertColourEquals(96, $samples[0]['red'], $tolerance);
$this->assertColourEquals(91, $samples[2]['red'], $tolerance);
$this->assertColourEquals(76, $samples[0]['red'], $tolerance);
$this->assertColourEquals(149, $samples[2]['red'], $tolerance);
$this->assertColourEquals(0, $samples[8]['red'], $tolerance);
$this->assertColourEquals(127, $samples[9]['red'], $tolerance);

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