imagecolorallocate
(PHP 4, PHP 5)
imagecolorallocate — Создание цвета для изображения
Описание
$image
, int $red
, int $green
, int $blue
)Возвращает идентификатор цвета в соответствии с заданными RGB компонентами.
imagecolorallocate() должна вызываться для создания
каждого цвета, который будет использоваться в изображении
image.
Замечание:
Первый вызов imagecolorallocate() задает цвет фона в палитровых изображениях - изображениях, созданных функцией imagecreate().
Список параметров
-
image -
Ресурс изображения, полученный одной из функций создания изображений, например, такой как imagecreatetruecolor().
-
red -
Значение красного компонента цвета.
-
green -
Значение зеленого компонента цвета.
-
blue -
Значение синего компонента цвета.
Возвращаемые значения
Идентификатор цвета, либо FALSE в случае неудачи.
Эта функция
может возвращать как boolean FALSE, так и не-boolean значение,
которое приводится к FALSE. За более подробной информацией обратитесь к разделу
Булев тип. Используйте оператор === для проверки значения,
возвращаемого этой функцией.
Список изменений
| Версия | Описание |
|---|---|
| 5.1.3 |
Возвращает FALSE в случае неудачи. В
предыдущих версиях в этом случае возвращалось
значение -1.
|
Примеры
Пример #1 Пример использования imagecolorallocate()
<?php
$im = imagecreate(100, 100);
// делаем фон красным
$background = imagecolorallocate($im, 255, 0, 0);
// создадим несколько цветов
$white = imagecolorallocate($im, 255, 255, 255);
$black = imagecolorallocate($im, 0, 0, 0);
// шестнадцатиричный способ
$white = imagecolorallocate($im, 0xFF, 0xFF, 0xFF);
$black = imagecolorallocate($im, 0x00, 0x00, 0x00);
?>
Смотрите также
- imagecolorallocatealpha() - Создание цвета для изображения
- imagecolordeallocate() - Разрыв ассоциации переменной с цветом для заданного изображения
- PHP Руководство
- Функции по категориям
- Индекс функций
- Справочник функций
- Обработка и генерация изображений
- Обработка изображений и GD
- gd_info
- getimagesize
- getimagesizefromstring
- image_type_to_extension
- image_type_to_mime_type
- image2wbmp
- imageaffine
- imageaffinematrixconcat
- imageaffinematrixget
- imagealphablending
- imageantialias
- imagearc
- imagechar
- imagecharup
- imagecolorallocate
- imagecolorallocatealpha
- imagecolorat
- imagecolorclosest
- imagecolorclosestalpha
- imagecolorclosesthwb
- imagecolordeallocate
- imagecolorexact
- imagecolorexactalpha
- imagecolormatch
- imagecolorresolve
- imagecolorresolvealpha
- imagecolorset
- imagecolorsforindex
- imagecolorstotal
- imagecolortransparent
- imageconvolution
- imagecopy
- imagecopymerge
- imagecopymergegray
- imagecopyresampled
- imagecopyresized
- imagecreate
- imagecreatefromgd2
- imagecreatefromgd2part
- imagecreatefromgd
- imagecreatefromgif
- imagecreatefromjpeg
- imagecreatefrompng
- imagecreatefromstring
- imagecreatefromwbmp
- imagecreatefromwebp
- imagecreatefromxbm
- imagecreatefromxpm
- imagecreatetruecolor
- imagecrop
- imagecropauto
- imagedashedline
- imagedestroy
- imageellipse
- imagefill
- imagefilledarc
- imagefilledellipse
- imagefilledpolygon
- imagefilledrectangle
- imagefilltoborder
- imagefilter
- imageflip
- imagefontheight
- imagefontwidth
- imageftbbox
- imagefttext
- imagegammacorrect
- imagegd2
- imagegd
- imagegif
- imagegrabscreen
- imagegrabwindow
- imageinterlace
- imageistruecolor
- imagejpeg
- imagelayereffect
- imageline
- imageloadfont
- imagepalettecopy
- imagepalettetotruecolor
- imagepng
- imagepolygon
- imagepsbbox
- imagepsencodefont
- imagepsextendfont
- imagepsfreefont
- imagepsloadfont
- imagepsslantfont
- imagepstext
- imagerectangle
- imagerotate
- imagesavealpha
- imagescale
- imagesetbrush
- imagesetinterpolation
- imagesetpixel
- imagesetstyle
- imagesetthickness
- imagesettile
- imagestring
- imagestringup
- imagesx
- imagesy
- imagetruecolortopalette
- imagettfbbox
- imagettftext
- imagetypes
- imagewbmp
- imagewebp
- imagexbm
- iptcembed
- iptcparse
- jpeg2wbmp
- png2wbmp
Коментарии
Actually, you can't allocate more than 256 colours for an paletted image (ImageCreate).Use ImageCreateTrueColor instead. For it to work, you need libgd version 2 support in php though.
I was unable to get any of the posted methods for converting colour to grayscale to work. The problem appears to be the way gd creates images from jpeg inconsistently over various versions. Eventually I wrote my own that works for me - this approach allocates the 256 color pallete first. You can also play with separate $r, $g, $b variables before using imagecolorallocate in order to tone or tint the image.
<?php
$resource = 'whatever.jpg';
$im_size = GetImageSize($resource);
$imageWidth = $im_size[0];
$imageHeight = $im_size[1];
$im = imageCreate($imageWidth,$imageHeight);
for ($c = 0; $c < 256; $c++) {
ImageColorAllocate($im, $c,$c,$c);
}
$im2 = ImageCreateFromJpeg($resource);
ImageCopyMerge($im,$im2,0,0,0,0, $imageWidth, $imageHeight, 100);
ImageDestroy($im2);
?>
go on using $im as your image, it is now grayscale ....
<?php
/*
An example combining the use of ImageColorAllocate, Imagesetpixel, Imagecopyresized and some basic Trig
*/
Header("Content-type: image/png");
$height = 128;
$width = 128;
$imA = ImageCreate($width, $height);
$imB = ImageCreate($width*4, $height*4);
$bckA = ImageColorAllocate($imA, 0,0,0);
$bckB = ImageColorAllocate($imB, 0,0,0);
//GENERATE GRAY SCALE PALLETE
for($c=0;$c<256;$c++){
ImageColorAllocate($imA, $c, $c, $c);
}
//PRODUCE DATA
$m=rand(0,10);
for($c=0;$c<128;$c++){
$s= (sin( deg2rad($c*360*$m/128) )+1)*127;
$col_arr[$c]=$s;
}
for($y=0;$y<$height;$y++){
for($x=0;$x<$width;$x++){
$imgA[$x][$y]=$col_arr[$x];
}
}
for($y=0;$y<$height;$y++){
for($x=0;$x<$width;$x++){
$imgB[$x][$y]=$col_arr[$y];
}
}
//SET PIXELS
for($y=0;$y<$height;$y++){
for($x=0;$x<$width;$x++){
$imgC[$x][$y]=$imgA[$x][$y]+$imgB[$x][$y];
$s=$imgC[$x][$y]/2;
Imagesetpixel($imA,$x,$y,$s);
}
}
//RESIZE IMAGE FOR DISPLAY
Imagecopyresized ($imB, $imA, 0, 0, 0, 0, $width*4, $height*4, $width, $width);
ImagePNG($imB);
?>
this might help someone, how to allocate an color from an html color-definition:
<?php
$fg = "#ff0080";
$red = 100;
$green = 100;
$blue = 100;
if( eregi( "[#]?([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})", $fg, $ret ) )
{
$red = hexdec( $ret[1] );
$green = hexdec( $ret[2] );
$blue = hexdec( $ret[3] );
}
$text_color = ImageColorAllocate( $img1, $red, $green, $blue );
?>
Some of you maybe want to use HSV color model for drawing color selectors and circles:
<?php
function &colormap_hsv_to_rgb($h, $s, $v)
{
$ret = new stdClass();
if($s == 0)
{
$ret->r = $v;
$ret->g = $v;
$ret->b = $v;
return $ret;
}
else
{
$h = floatval($h) / 255.0;
$s = floatval($s) / 255.0;
$v = floatval($v) / 255.0;
$hue = $h;
if($hue == 1.0)
$hue = 0.0;
$hue *= 6.0;
$i = intval($hue);
$f = $hue - floatval($i);
$w = $v * (1.0 - $s);
$q = $v * (1.0 - ($s * $f));
$t = $v * (1.0 - ($s * (1.0 - $f)));
switch($i)
{
case 0: $ret->r = $v; $ret->g = $t; $ret->b = $w; break;
case 1: $ret->r = $q; $ret->g = $v; $ret->b = $w; break;
case 2: $ret->r = $w; $ret->g = $v; $ret->b = $t; break;
case 3: $ret->r = $w; $ret->g = $q; $ret->b = $v; break;
case 4: $ret->r = $t; $ret->g = $w; $ret->b = $v; break;
case 5: $ret->r = $v; $ret->g = $w; $ret->b = $q; break;
}
}
$ret->r = intval($ret->r * 255.0);
$ret->g = intval($ret->g * 255.0);
$ret->b = intval($ret->b * 255.0);
return $ret;
}
?>
2 functions to convert from HSV colorspace (hue/saturation/brightness) to RGB (red/green/blue) colorspace and back.
<?php
// $c = array($red, $green, $blue)
// $red=[0..1], $green=[0..1], $blue=[0..1];
function rgb2hsv($c) {
list($r,$g,$b)=$c;
$v=max($r,$g,$b);
$t=min($r,$g,$b);
$s=($v==0)?0:($v-$t)/$v;
if ($s==0)
$h=-1;
else {
$a=$v-$t;
$cr=($v-$r)/$a;
$cg=($v-$g)/$a;
$cb=($v-$b)/$a;
$h=($r==$v)?$cb-$cg:(($g==$v)?2+$cr-$cb:(($b==$v)?$h=4+$cg-$cr:0));
$h=60*$h;
$h=($h<0)?$h+360:$h;
}
return array($h,$s,$v);
}
// $c = array($hue, $saturation, $brightness)
// $hue=[0..360], $saturation=[0..1], $brightness=[0..1]
function hsv2rgb($c) {
list($h,$s,$v)=$c;
if ($s==0)
return array($v,$v,$v);
else {
$h=($h%=360)/60;
$i=floor($h);
$f=$h-$i;
$q[0]=$q[1]=$v*(1-$s);
$q[2]=$v*(1-$s*(1-$f));
$q[3]=$q[4]=$v;
$q[5]=$v*(1-$s*$f);
//return(array($q[($i+4)%5],$q[($i+2)%5],$q[$i%5]));
return(array($q[($i+4)%6],$q[($i+2)%6],$q[$i%6])); //[1]
}
}
?>
[1] - EDITOR NOTE: THIS IS A FIX FROM "hc at hob(removethis)soft dot net".
This will let you tint an image to any specific color. The blacks of the source image become your specified color, and the whites remain white. Works best for colorizing greyscale images.
<?php
$r = 224;
$g = 192;
$b = 0;
$source_file = "picture.jpg";
$im_src = ImageCreateFromJpeg($source_file);
$im_tint = ImageCreate(imagesx($im_src),imagesy($im_src));
for ($c = 0; $c < 255; $c++) {
ImageColorAllocate($im_tint, max($r,$c), max($g,$c), max($b,$c));
}
ImageCopyMerge($im_tint,$im_src,0,0,0,0, imagesx($im_src), imagesy($im_src), 100);
ImageDestroy($im_src);
header("Content-type: image/jpeg");
imagejpeg($im_tint);
?>
When you are using truecolor images, you can also use bitwise operations to generate the color:<?php
$color = ($r << 16) | ($g << 8) | $b; // 2261213
?>
This is identical to the imagecolorallocate() function, in truecolor images!
<?php
/**
* Create a image bar using lib GD
* Ege. <img src="color_sample.php?color=FF0000" width="10 height="30">
*/
// Split the HTML color representation
$hexcolor = str_split($_GET["color"], 2);
// Convert HEX values to DECIMAL
$bincolor[0] = hexdec("0x{$hexcolor[0]}");
$bincolor[1] = hexdec("0x{$hexcolor[1]}");
$bincolor[2] = hexdec("0x{$hexcolor[2]}");
$im = ImageCreate(100, 100);
$colorallocate = ImageColorAllocate($im, $bincolor[0], $bincolor[1], $bincolor[2]);
ImageFilledRectangle($im, 0, 0, 100, 100, $colorallocate);
header('Content-Type: image/png');
ImagePNG($im);
?>
hsl to RGB
(not yet optimized but it function)
<?php
function hslToRgb ($h, $s, $l) {
if ($h>240 || $h<0) return array(0,0,0);
if ($s>240 || $s<0) return array(0,0,0);
if ($l>240 || $l<0) return array(0,0,0);
if ($h<=40) {
$R=255;
$G=(int)($h/40*256);
$B=0;
}
elseif ($h>40 && $h<=80) {
$R=(1-($h-40)/40)*256;
$G=255;
$B=0;
}
elseif ($h>80 && $h<=120) {
$R=0;
$G=255;
$B=($h-80)/40*256;
}
elseif ($h>120 && $h<=160) {
$R=0;
$G=(1-($h-120)/40)*256;
$B=255;
}
elseif ($h>160 && $h<=200) {
$R=($h-160)/40*256;
$G=0;
$B=255;
}
elseif ($h>200) {
$R=255;
$G=0;
$B=(1-($h-200)/40)*256;
}
$R=$R+(240-$s)/240*(128-$R);
$G=$G+(240-$s)/240*(128-$G);
$B=$B+(240-$s)/240*(128-$B);
if ($l<120) {
$R=($R/120)*$l;
$G=($G/120)*$l;
$B=($B/120)*$l;
}
else {
$R=$l*((256-$R)/120)+2*$R-256;
$G=$l*((256-$G)/120)+2*$G-256;
$B=$l*((256-$B)/120)+2*$B-256;
}
if ($R<0) $R=0;
if ($R>255) $R=255;
if ($G<0) $G=0;
if ($G>255) $G=255;
if ($B<0) $B=0;
if ($B>255) $B=255;
return array((int)$R,(int)$G,(int)$B);
}
?>
This nifty function will produce the negative of a given image!
<?php
/********************************
Code by Kailash Nadh
http://kailashnadh.name
usage:
img2neg("my_pic.jpg");
*********************************/
function img2neg($pic) {
header("Content-type: image/jpeg");
$source=imagecreatefromjpeg($pic); // Source
$width=imagesx($source); $height=imagesy($source);
$im = imagecreatetruecolor($width, $height); // Our negative img in the making
for($y=0; $y < $height; $y++) {
for($x=0; $x < $width; $x++) {
$colors=imagecolorsforindex($source, imagecolorat($source, $x,$y));
// this is what makes the colors negative
$r=255-$colors['red'];
$g=255-$colors['green'];
$b=255-$colors['blue'];
$test=imagecolorallocate($im, $r,$g,$b);
imagesetpixel($im,$x, $y, $test);
}
}
imagejpeg($im);
imagedestroy($im);
}
?>
Here's a very simple and very effective code to change a HEX color to RGB.
<?php
function HEX2RGB($color){
$color_array = array();
$hex_color = strtoupper($color);
for($i = 0; $i < 6; $i++){
$hex = substr($hex_color,$i,1);
switch($hex){
case "A": $num = 10; break;
case "B": $num = 11; break;
case "C": $num = 12; break;
case "D": $num = 13; break;
case "E": $num = 14; break;
case "F": $num = 15; break;
default: $num = $hex; break;
}
array_push($color_array,$num);
}
$R = (($color_array[0] * 16) + $color_array[1]);
$G = (($color_array[2] * 16) + $color_array[3]);
$B = (($color_array[4] * 16) + $color_array[5]);
return array($R,$G,$B);
unset($color_array,$hex,$R,$G,$B);
}
?>
Another more general variation on the theme using the same naming conventions as the hexdec and dechex built-in functions ...
Prototype:
array hexrgb ( string hex_string )
Returns:
An associative array of the RGB components specified in hex_string.
hexrgb() example:
<?php
$rgb = hexrgb("0xAABBCC");
print_r($rgb);
?>
Output is:
Array
(
[red] => 170
[green] => 187
[blue] => 204
)
Implementation:
<?php
function hexrgb ($hexstr)
{
$int = hexdec($hexstr);
return array("red" => 0xFF & ($int >> 0x10),
"green" => 0xFF & ($int >> 0x8),
"blue" => 0xFF & $int);
}
?>
The output of hexdec can then be passed to imagecolorallocate and manipulated as required.
This works! A Black-Image with vertical centered white Aliased Arial-Text and same left and right margin - used for Menu-Buttons.
<?php
function createImgText ($string="", $fontsize=0, $marginX=0, $imgH=0 , $fontfile="", $imgColorHex="", $txtColorHex=""){
if($string!=""){
Header("Content-type: image/png");
//
$spacing = 0;
$line = array("linespacing" => $spacing);
$box = @imageftbbox($fontsize,0,$fontfile,$string,$line)
or die("ERROR");
$tw=$box[4]-$box[0]; //image width
$marginY = $imgH - (($imgH - $fontsize) / 2);
$imgWidth = $tw + (2*$marginX);
$im = ImageCreate($imgWidth, $imgH);
$int = hexdec($imgColorHex);
$arr = array("red" => 0xFF & ($int >> 0x10),
"green" => 0xFF & ($int >> 0x8),
"blue" => 0xFF & $int);
$black = ImageColorAllocate($im, $arr["red"], $arr["green"], $arr["blue"]);
$int = hexdec($txtColorHex);
$arr = array("red" => 0xFF & ($int >> 0x10),
"green" => 0xFF & ($int >> 0x8),
"blue" => 0xFF & $int);
$white = ImageColorAllocate($im, $arr["red"], $arr["green"], $arr["blue"]);
ImageFtText($im, $fontsize, 0, $marginX, $marginY, $white, $fontfile, $string, array());
ImagePng($im);
ImageDestroy($im);
}else{
echo "ERROR!";
}
}
createImgText ("Hello World", 9, 10, 18, "arial.ttf", "000000", "FFFFFF");
?>
Also, when you need more then 256 colors, use imagecreatetruecolor function. With this function you can use unlimited number of colors.Another solution to color limitation issues when creating gradients. This file takes width (px) and left and right colors (hex) and makes a gradient while only allocating 250 colors.
<?php
$leftR = hexdec(substr($_GET["left"],0,2));
$leftG = hexdec(substr($_GET["left"],2,2));
$leftB = hexdec(substr($_GET["left"],4,2));
$rightR = hexdec(substr($_GET["right"],0,2));
$rightG = hexdec(substr($_GET["right"],2,2));
$rightB = hexdec(substr($_GET["right"],4,2));
$image=imagecreate($_GET["width"],1);
for($i=0;$i<250;$i++) {
$colorset[$i] = imagecolorallocate($image, $leftR + ($i*(($rightR-$leftR)/250)), $leftG + ($i*(($rightG-$leftG)/250)), $leftB + ($i*(($rightB-$leftB)/250)));
}
for($i=0;$i<($_GET["width"]);$i++) {
imagesetpixel ($image, $i, 0, $colorset[(int)($i/($_GET["width"]/250))] );
}
header("Content-type: image/png");
imagepng($image);
imagedestroy($image);
?>
example: gradient.php?width=640&left=000000&right=FF0000
Makes a 640px-wide image that fades from black to red.
Lots of hsv2rgb commentary but no working example, so here's mine:
<?php // hsv2rgb example translated from ImageMagick C code
function hsv2rgb($h, $s, $v)
{
$s /= 256.0;
if ($s == 0.0) return array($v,$v,$v);
$h /= (256.0 / 6.0);
$i = floor($h);
$f = $h - $i;
$p = (integer)($v * (1.0 - $s));
$q = (integer)($v * (1.0 - $s * $f));
$t = (integer)($v * (1.0 - $s * (1.0 - $f)));
switch($i) {
case 0: return array($v,$t,$p);
case 1: return array($q,$v,$p);
case 2: return array($p,$v,$t);
case 3: return array($p,$q,$v);
case 4: return array($t,$p,$v);
default: return array($v,$p,$q);
}
}
$image = ImageCreateTrueColor(256,128);
for ($y=0; $y<64; $y++) for($x=0; $x<256; $x++){
list($r,$g,$b) = hsv2rgb($x | 7,255,($y*4) |7);
$color = ($r << 16 ) | ($g << 8) | $b;
imagesetpixel($image, $x, $y-4, $color);
}
for ($y=64; $y<128; $y++) for($x=0; $x<256; $x++){
list($r,$g,$b) = hsv2rgb($x|7,((127-$y)*4)|7,255);
$color = ($r << 16) | ($g << 8) | $b;
imagesetpixel($image, $x, $y-4, $color);
}
for ($y=120; $y<128; $y++) for($x=0; $x<256; $x++){
$color = (($x |7) << 16) | (($x |7) << 8) | ($x |7);
imagesetpixel($image, $x, $y, $color);
}
header("Content-Type: image/png");
imagepng($image);
?>
When working on an existant GIF images, if the number of different colours has reached the limits of the GIF format, imagecolorallocate will not use to the colour you ask her within the parameters, she will apply black !
That's a problem when generating images "on-the-fly" with many manipulations, from a GIF image.
To go round the problem, you have to convert the GIF image into a PNG one, and then you can work on the PNG and everything will be ok.
For example :
<?php
// first, convert into a PNG image
$handle = imagecreatefromgif('my_image.gif');
imagepng($handle, 'my_image.png');
imagedestroy($handle);
// then, you can work on it
$handle = imagecreatefrompng('my_image.png');
/*
* work on the image
*/
imagegif($handle);
?>
Note that you can only assign 255 colors to any image palette. If you try assigning more, imagecolorallocate() will fail.
If, for example, you are randomly allocating colors, it will be wise to check if you have used up all of the colors possible. You can use imagecolorclosest() to get the closest assigned color:
<?php
//assign random rgb values
$c1 = mt_rand(50,200); //r(ed)
$c2 = mt_rand(50,200); //g(reen)
$c3 = mt_rand(50,200); //b(lue)
//test if we have used up palette
if(imagecolorstotal($pic)>=255) {
//palette used up; pick closest assigned color
$color = imagecolorclosest($pic, $c1, $c2, $c3);
} else {
//palette NOT used up; assign new color
$color = imagecolorallocate($pic, $c1, $c2, $c3);
}
?>
Also, imagecolorallocate() will assign a new color EVERY time the function is called, even if the color already exists in the palette:
<?php
// [...]
imagecolorallocate($pic,125,125,125); //returns 5
imagecolorallocate($pic,125,125,125); //returns 6
imagecolorallocate($pic,125,125,125); //returns 7
// [...]
imagecolorallocate($pic,125,125,125); //returns 23
imagecolorallocate($pic,125,125,125); //returns 25
// [...]
// etc...
?>
So here, imagecolorexact() is useful:
<?php
//see if color already exists
$color = imagecolorexact($pic, $c1, $c2, $c3);
if($color==-1) {
//color does not exist; allocate a new one
$color = imagecolorallocate($pic, $c1, $c2, $c3);
}
?>
And, for nerdy-ness sake, we can put the two ideas together:
<?php
//assign random rgb values
$c1 = mt_rand(50,200); //r(ed)
$c2 = mt_rand(50,200); //g(reen)
$c3 = mt_rand(50,200); //b(lue)
//get color from palette
$color = imagecolorexact($pic, $c1, $c2, $c3);
if($color==-1) {
//color does not exist...
//test if we have used up palette
if(imagecolorstotal($pic)>=255) {
//palette used up; pick closest assigned color
$color = imagecolorclosest($pic, $c1, $c2, $c3);
} else {
//palette NOT used up; assign new color
$color = imagecolorallocate($pic, $c1, $c2, $c3);
}
}
?>
Or as a function:
<?php
function createcolor($pic,$c1,$c2,$c3) {
//get color from palette
$color = imagecolorexact($pic, $c1, $c2, $c3);
if($color==-1) {
//color does not exist...
//test if we have used up palette
if(imagecolorstotal($pic)>=255) {
//palette used up; pick closest assigned color
$color = imagecolorclosest($pic, $c1, $c2, $c3);
} else {
//palette NOT used up; assign new color
$color = imagecolorallocate($pic, $c1, $c2, $c3);
}
}
return $color;
}
for($i=0; $i<1000; $i++) { //1000 because it is significantly greater than 255
//assign random rgb values
$c1 = mt_rand(50,200); //r(ed)
$c2 = mt_rand(50,200); //g(reen)
$c3 = mt_rand(50,200); //b(lue)
//generate the color
$color = createcolor($pic,$c1,$c2,$c3);
//do something with color...
}
?>
If you even in a situation where it's not allocating the color you want it could be because of your images color allocation table. GIF and 8-bit PNG images are very susceptible to this.
If your using an GIF and PNG try dropping a color from the table, should let you allocate another.
you have VERY limited space for color indexes (255 indexes on my system, with over 10 GB ram available, cli, no memory limit), when there is no more indexes available, imagecolorallocate will return false. when you create 2x indexes with the same r/g/b, you waste this very limited space. the function below should never fail, AND never waste any color index space. if there's already an index with the rgb, it will return the existing index, else it will try allocate 1, in the event that allocation fail (presumably because all index space is used up already), it will return the closest match to what you requested, and warn you via $couldFindExact.
function myimagecolorallocate($gd,int $red,int $green,int $blue,bool &$couldFindExact=null):int{
$ret=imagecolorexact($gd, $red, $green, $blue);
if($ret===-1){
$ret=imagecolorallocate($gd, $red, $green, $blue);
if($ret===false){
$couldFindExact=false;//out of color indexes (255 index by default..wish i knew why)
$ret=imagecolorclosest($gd, $red, $green, $blue);
} else {
$couldFindExact=true;
}
} else {
$couldFindExact=true;
}
return $ret;
}