Question

如何编写一个CGA着色器，将调色板限制为4种颜色，并将原始颜色与那些（青色，品红色，黑色，白色）相匹配？

我正在使用Game Maker Studio Professional，它实际上允许使用着色器编写顶点和片段代码

我已经在yoyogames社区和openGl论坛中提出了这个问题

有人用这个回答我：

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);
}

它有效，但不返回cga调色板，它返回黑白（不是灰度）

我该怎么办？

Answer 1

非常感谢我用不同的方式做了，也许更简单

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

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

/*

////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;
}

这里我还包括将这个shadertoy着色器转换为游戏制作工作室着色器的方法，因为在游戏制作工作室中没有统一的时间和分辨率来进行时间编辑和vec2 uv

我还包括所有cga调色板的评论右调色板和奖金调色板0，它是一个gameboy调色板

我还包括从rgb 255值转换为无法转换的浮点数

这里唯一的问题是它无法反转颜色或改变调色板中颜色的位置，它采用原始光源并输出4种颜色，这是唯一的差距。

如何在glsl中编写cga着色器？

1 个答案: