使用着色器将 RGB 转为 YUV

Question

我想使用片段着色器，使用着色器将 RGB 转换为 YUV420P。

1，我算出了当前贴图颜色的坐标

2，我计算了4个Y放在当前颜色上

我的代码：

    precision mediump float;
    varying vec2 vTextureCoord;
    uniform sampler2D tex;
    uniform float width;
    uniform float height;
    uniform float offset;
    uniform vec3 scal;

    void main(void) {
        vec2 nowTxtPos = vTextureCoord;
        vec2 size = vec2(width, height);
    // y
        if(nowTxtPos.y<0.25){
    // y1 postion
            vec2 now_pos = nowTxtPos * size;
            vec2 basePos = now_pos * vec2(4.0,4.0);
            float addY = float(int(basePos.x / width));
            basePos.x = basePos.x - addY * width;
            basePos.y += addY;

            float y1,y2,y3,y4;
            vec2 samplingPos = basePos / size;
            vec4 texel = texture2D(tex, samplingPos);
            y1 = dot(texel.rgb, scal);
            y1 += offset;

            basePos.x+=1.0;
            samplingPos = basePos/size;
            texel = texture2D(tex, samplingPos);
            y2 = dot(texel.rgb, scal);
            y2 += offset;

            basePos.x+=1.0;
            samplingPos = basePos/size;
            texel = texture2D(tex, samplingPos);
            y3 = dot(texel.rgb, scal);
            y3 += offset;

            basePos.x+=1.0;
            samplingPos = basePos/size;
            texel = texture2D(tex, samplingPos);
            y4 = dot(texel.rgb, scal);
            y4 += offset;

            gl_FragColor = vec4(y1, y2, y3, y4);
        }
    }

图片(YUV420P):

picture

Enlarged post picture

它有别名。不知道为什么。

Answer 1

我已经解决了。因为计算精度不够

在此处编辑：

"precision mediump float;" -> "precision highp float;"

使用着色器将 RGB 转为 YUV

RGB to YUV using shader

opengl

rgb

shader

glsl

yuv