在 PHP 中从图像生成调色板

Question

I need to create color palette with PHP. I use code like this:

for ($x = 0; $x < $this->width; $x += $level) {
    for ($y = 0; $y < $this->height; $y += $level) {
        $index = imagecolorat($this->workingImage, $x, $y);
        $rgb = imagecolorsforindex($this->workingImage, $index);
        $color = $this->getClosestColor($rgb["red"], $rgb["green"], $rgb["blue"]);
        $hexarray[] = $this->RGBToHex($color[0], $color[1], $color[2]);
    }
}

How can I do it? For any picture I need at least 10 colors. I am tried to use another methods, pixelate image before receiving color palette, but it is not helping for me.

Answer 1

Unfortunately you have mixed up your starting image with your incorrect results and your desired results, so I have separated it out as image.png below:

Now, I plan to use pnmquant which is part of the NetPBM package which is available precompiled and ready to install on most platforms from SourceForge.

So, first I need to convert your PNG to NetPBM's PPM format for the pnmquant tool to work - I'll use pngtopnm for that. Then I want to extract the colours as a swatch and enlarge the swatch so you can see something bigger than the extracted 21 pixels -I'll use ImageMagick for that, and I want to make a text representation of it so you can see the numbers, and I'll use ImageMagick for that.

pngtopnm image.png | pnmquant 21 | pnmtopng > result.png

convert image.png pnm:- | pnmquant 21 | convert - -unique-colors -scale 400x swatch.png

convert image.png pnm:- | pnmquant 21 | convert - -unique-colors -depth 8 txt:

# ImageMagick pixel enumeration: 21,1,65535,srgb
0,0: (65278,9766,2827)  #FE260B  srgb(254,38,11)
1,0: (65278,15163,2570)  #FE3B0A  srgb(254,59,10)
2,0: (65535,10794,5140)  #FF2A14  srgb(255,42,20)
3,0: (65535,11565,5140)  #FF2D14  srgb(255,45,20)
4,0: (65278,11308,5140)  #FE2C14  srgb(254,44,20)
5,0: (65535,11822,5140)  #FF2E14  srgb(255,46,20)
6,0: (65278,11822,5140)  #FE2E14  srgb(254,46,20)
7,0: (65278,19532,3341)  #FE4C0D  srgb(254,76,13)
8,0: (65278,20817,3855)  #FE510F  srgb(254,81,15)
9,0: (65278,16962,5140)  #FE4214  srgb(254,66,20)
10,0: (65535,20303,4369)  #FF4F11  srgb(255,79,17)
11,0: (65278,20817,4626)  #FE5112  srgb(254,81,18)
12,0: (63479,33410,28270)  #F7826E  srgb(247,130,110)
13,0: (62451,56540,55769)  #F3DCD9  srgb(243,220,217)
14,0: (62708,61166,59110)  #F4EEE6  srgb(244,238,230)
15,0: (62451,62708,62965)  #F3F4F5  srgb(243,244,245)
16,0: (65278,63736,62965)  #FEF8F5  srgb(254,248,245)
17,0: (62194,65278,65535)  #F2FEFF  srgb(242,254,255)
18,0: (65278,64250,63736)  #FEFAF8  srgb(254,250,248)
19,0: (65535,65535,65535)  #FFFFFF  white
20,0: (65278,65278,65278)  #FEFEFE  srgb(254,254,254)

As regards PHP, you can shell out and exec the command-line tools above, or look at the source code and adapt to PHP.