Android GPUImage-17: 3x3 Convolution

最新推荐文章于 2025-11-24 17:06:11 发布

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#android #图形渲染

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该文章介绍了一种使用OpenGL着色器（shader）进行图像处理的方法，特别是通过3x3的卷积矩阵对周围9个像素点进行操作，以改变图像的视觉效果。着色器代码涉及了纹理坐标和从输入纹理中采样颜色的步骤，最终将计算后的颜色赋值给新的像素点。

1.效果图

2.shader

 "precision highp float;\n" +
            "\n" +
            "uniform sampler2D inputImageTexture;\n" +
            "\n" +
            "uniform mediump mat3 convolutionMatrix;\n" +
            "\n" +
            "varying vec2 textureCoordinate;\n" +
            "varying vec2 leftTextureCoordinate;\n" +
            "varying vec2 rightTextureCoordinate;\n" +
            "\n" +
            "varying vec2 topTextureCoordinate;\n" +
            "varying vec2 topLeftTextureCoordinate;\n" +
            "varying vec2 topRightTextureCoordinate;\n" +
            "\n" +
            "varying vec2 bottomTextureCoordinate;\n" +
            "varying vec2 bottomLeftTextureCoordinate;\n" +
            "varying vec2 bottomRightTextureCoordinate;\n" +
            "\n" +
            "void main()\n" +
            "{\n" +
            "    mediump vec4 bottomColor = texture2D(inputImageTexture, bottomTextureCoordinate);\n" +
            "    mediump vec4 bottomLeftColor = texture2D(inputImageTexture, bottomLeftTextureCoordinate);\n" +
            "    mediump vec4 bottomRightColor = texture2D(inputImageTexture, bottomRightTextureCoordinate);\n" +
            "    mediump vec4 centerColor = texture2D(inputImageTexture, textureCoordinate);\n" +
            "    mediump vec4 leftColor = texture2D(inputImageTexture, leftTextureCoordinate);\n" +
            "    mediump vec4 rightColor = texture2D(inputImageTexture, rightTextureCoordinate);\n" +
            "    mediump vec4 topColor = texture2D(inputImageTexture, topTextureCoordinate);\n" +
            "    mediump vec4 topRightColor = texture2D(inputImageTexture, topRightTextureCoordinate);\n" +
            "    mediump vec4 topLeftColor = texture2D(inputImageTexture, topLeftTextureCoordinate);\n" +
            "\n" +
            "    mediump vec4 resultColor = topLeftColor * convolutionMatrix[0][0] + topColor * convolutionMatrix[0][1] + topRightColor * convolutionMatrix[0][2];\n" +
            "    resultColor += leftColor * convolutionMatrix[1][0] + centerColor * convolutionMatrix[1][1] + rightColor * convolutionMatrix[1][2];\n" +
            "    resultColor += bottomLeftColor * convolutionMatrix[2][0] + bottomColor * convolutionMatrix[2][1] + bottomRightColor * convolutionMatrix[2][2];\n" +
            "\n" +
            "    gl_FragColor = resultColor;\n" +

3.原理

是周围的9个点乘以3x3的矩阵。