Android GPUImage-5: Weak Pixel Inclusion-优快云博客

本文链接：https://blog.youkuaiyun.com/codemydream/article/details/129753882

该代码段展示了一个OpenGL着色器，用于检测图像中像素的强度。它获取9个相邻像素的R值之和，如果超过1.5且中心像素值大于0.01，那么该位置像素会被保留。这个过程涉及到纹理坐标、步长计算以及像素测试。

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效果图

shader

"attribute vec4 position;\n" +
            "attribute vec4 inputTextureCoordinate;\n" +
            "\n" +
            "uniform highp float texelWidth; \n" +
            "uniform highp float texelHeight; \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" +
            "    gl_Position = position;\n" +
            "\n" +
            "    vec2 widthStep = vec2(texelWidth, 0.0);\n" +
            "    vec2 heightStep = vec2(0.0, texelHeight);\n" +
            "    vec2 widthHeightStep = vec2(texelWidth, texelHeight);\n" +
            "    vec2 widthNegativeHeightStep = vec2(texelWidth, -texelHeight);\n" +
            "\n" +
            "    textureCoordinate = inputTextureCoordinate.xy;\n" +
            "    leftTextureCoordinate = inputTextureCoordinate.xy - widthStep;\n" +
            "    rightTextureCoordinate = inputTextureCoordinate.xy + widthStep;\n" +
            "\n" +
            "    topTextureCoordinate = inputTextureCoordinate.xy - heightStep;\n" +
            "    topLeftTextureCoordinate = inputTextureCoordinate.xy - widthHeightStep;\n" +
            "    topRightTextureCoordinate = inputTextureCoordinate.xy + widthNegativeHeightStep;\n" +
            "\n" +
            "    bottomTextureCoordinate = inputTextureCoordinate.xy + heightStep;\n" +
            "    bottomLeftTextureCoordinate = inputTextureCoordinate.xy - widthNegativeHeightStep;\n" +
            "    bottomRightTextureCoordinate = inputTextureCoordinate.xy + widthHeightStep;\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" +
            "uniform sampler2D inputImageTexture;\n" +
            "\n" +
            "void main()\n" +
            "{\n" +
            "float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;\n" +
            "float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;\n" +
            "float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;\n" +
            "float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;\n" +
            "float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;\n" +
            "float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;\n" +
            "float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;\n" +
            "float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;\n" +
            "float centerIntensity = texture2D(inputImageTexture, textureCoordinate).r;\n" +
            "\n" +
            "float pixelIntensitySum = bottomLeftIntensity + topRightIntensity + topLeftIntensity + bottomRightIntensity + leftIntensity + rightIntensity + bottomIntensity + topIntensity + centerIntensity;\n" +
            "float sumTest = step(1.5, pixelIntensitySum);\n" +
            "float pixelTest = step(0.01, centerIntensity);\n" +
            "\n" +
            "gl_FragColor = vec4(vec3(sumTest * pixelTest), 1.0);\n" +
            "}\n";