如何在glsl中编写cga着色器？

问题描述：

如何编写CGA着色器，将调色板限制为4种颜色，并将原始颜色与那些颜色（青色，品红色，黑色，白色）相匹配？如何在glsl中编写cga着色器？

我工作的游戏制作工作室专业，实际上允许使用着色器编写顶点和片段代码的

我已经问过这个问题也是在yoyogames社区和OpenGL的论坛

人回答我这个：

varying vec2 v_vTexcoord; 
varying vec4 v_vColour; 

const mat3 rgb_to_wcm = mat3(1,-1, 0, 1, 0,-1, -1, 1, 1); 

void main() 
{ 
    vec4 rgba = v_vColour * texture2D(gm_BaseTexture, v_vTexcoord); 
    vec3 wcm = rgb_to_wcm * rgba.rgb; 
    vec3 rgb = dot(wcm,vec3(1,1,1)) < 0.5 
     ? vec3(0,0,0) 
     : wcm.x > wcm.y 
      ? (wcm.x > wcm.z ? vec3(1,1,1) : vec3(1,0,1)) 
      : (wcm.y > wcm.z ? vec3(0,1,1) : vec3(1,0,1)); 
    gl_FragColor = vec4(rgb, rgba.a); 
}

它的工作原理，但不会返回CGA调色板，它返回一个黑白（未灰度）

我该怎么办？

答

非常感谢我以不同的方式，也许更简单的做

https://www.shadertoy.com/view/MdlyDH

// ▄████████ ▄██████▄  ▄████████ 
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// ███  ▀▀███ ████▄ ▀███████████ 
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// ███ ███ ███ ███ ███ ███ 
// ████████▀ ████████▀ ███ █▀ 
// 

/* 

////only for game maker studio//// 

varying vec2 v_vTexcoord; 
varying vec4 v_vColour; 

varying vec2 fragCoord; 
//you have to put varying vec2 fragCoord also in the vertex shader 
//after write in the last row of the local scope of the vertex shader: fragCoord = in_Position.xy 

uniform vec2 iResolution; 
uniform float iGlobalTime; 

//palette 0 is not cga but gameboy, I put it as bonus 
uniform int palette; 
uniform float gamma; 

*/ 

// rgb to float 
// rgb to float = rgb/255 

// 0 = 0.0 
// 85 = 0.333 
// 170 = 0.666 
// 255 = 1.0 

void mainImage(out vec4 fragColor, in vec2 fragCoord) 
{ 
    vec2 uv = fragCoord.xy/iResolution.xy; 

    vec3 c = vec3(0.0); 
    float alpha = 1.0; 

    //only for shadertoy 
    int palette = 2; //the number between 0 and 6 change palette 
    float gamma = 1.5; //the gamma change the threshold of the palette swapper 

    //c = texture2D(gm_BaseTexture,uv).rgb; 
    c = texture(iChannel0,uv).rgb; 

    c.r = pow(abs(c.r),gamma); 
    c.g = pow(abs(c.g),gamma); 
    c.b = pow(abs(c.b),gamma); 

    vec3 col1 = vec3(0.0); 
    vec3 col2 = vec3(0.0); 
    vec3 col3 = vec3(0.0); 
    vec3 col4 = vec3(0.0); 

    if(palette == 0) { 
     col1 = vec3(0.612,0.725,0.086); 
     col2 = vec3(0.549,0.667,0.078); 
     col3 = vec3(0.188,0.392,0.188); 
     col4 = vec3(0.063,0.247,0.063); 
    } 
    if(palette == 1) { 
     col1 = vec3(0.0); 
     col2 = vec3(0.0,0.666,0.666); 
     col3 = vec3(0.666,0.0,0.666); 
     col4 = vec3(0.666,0.666,0.666); 
    } 
    if(palette == 2) { 
     col1 = vec3(0.0); 
     col2 = vec3(0.333,1.0,1.0); 
     col3 = vec3(1.0,0.333,1.0); 
     col4 = vec3(1.0); 
    } 
    if(palette == 3) { 
     col1 = vec3(0.0); 
     col2 = vec3(0.0,0.666,0.0); 
     col3 = vec3(0.666,0.0,0.0); 
     col4 = vec3(0.666,0.333,0.0); 
    } 
    if(palette == 4) { 
     col1 = vec3(0.0); 
     col2 = vec3(0.333,1.0,0.333); 
     col3 = vec3(1.0,0.333,0.333); 
     col4 = vec3(1.0,1.0,0.333); 
    } 
    if(palette == 5) { 
     col1 = vec3(0.0); 
     col2 = vec3(0.0,0.666,0.666); 
     col3 = vec3(0.666,0.0,0.0); 
     col4 = vec3(0.666,0.666,0.666); 
    } 
    if(palette == 6) { 
     col1 = vec3(0.0); 
     col2 = vec3(0.333,0.666,0.666); 
     col3 = vec3(1.0,0.333,0.333); 
     col4 = vec3(1.0); 
    } 

    float dist1 = length(c - col1); 
    float dist2 = length(c - col2); 
    float dist3 = length(c - col3); 
    float dist4 = length(c - col4); 

    float d = min(dist1,dist2); 
    d = min(d,dist3); 
    d = min(d,dist4); 

    if(d == dist1) { 
     c = col1; 
    } 
    else if(d == dist2) { 
     c = col2; 
    } 
    else if(d == dist3) { 
     c = col3; 
    } 
    else { 
     c = col4; 
    } 

    //gl_FragColor = vec4(c,alpha).rgba; 
    fragColor = vec4(c,alpha).rgba; 
}

我在这里也包括这个shadertoy着色器转换为游戏厂商工作室着色器，因为在路上游戏制作工作室有没有统一的时间和分辨率来进行时间编辑和vec2我还包括所有cga调色板的注释右调色板和奖金调色板0这是一个GAMEBOY调色板

我还包括从RGB值为255至浮子谁没有可能能够转换

这里唯一的问题是，它不能够反转颜色或改变位置的转换在调色板中的颜色，它需要原始的来源和输出4种颜色，这是唯一的差距。

如何在glsl中编写cga着色器？

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