色键 Chroma Key

整理下色键代码

ffmpeg 

typedef struct ColorkeyContext {    const AVClass *class;    /* color offsets rgba */    int co[4];    uint8_t colorkey_rgba[4];    float similarity;    float blend;} ColorkeyContext;static uint8_t do_colorkey_pixel(ColorkeyContext *ctx, uint8_t r, uint8_t g, uint8_t b){    int dr = (int)r - ctx->colorkey_rgba[0];    int dg = (int)g - ctx->colorkey_rgba[1];    int db = (int)b - ctx->colorkey_rgba[2];    double diff = sqrt((dr * dr + dg * dg + db * db) / (255.0 * 255.0));    if (ctx->blend > 0.0001) {        return av_clipd((diff - ctx->similarity) / ctx->blend, 0.0, 1.0) * 255.0;    } else {        return (diff > ctx->similarity) ? 255 : 0;    }}

gpuimage

// from: https://github.com/BradLarson/GPUImage/blob/master/framework/Source/GPUImageChromaKeyFilter.m#ifdef GL_ESprecision mediump float;precision mediump int;#endif#define PROCESSING_TEXTURE_SHADERuniform sampler2D texture;varying vec4 vertColor;varying vec4 vertTexCoord;uniform float thresholdSensitivity;uniform float smoothing;uniform vec3 colorToReplace;void main(){    vec4 textureColor = texture2D(texture, vertTexCoord.xy);        float maskY = 0.2989 * colorToReplace.r + 0.5866 * colorToReplace.g + 0.1145 * colorToReplace.b;    float maskCr = 0.7132 * (colorToReplace.r - maskY);    float maskCb = 0.5647 * (colorToReplace.b - maskY);        float Y = 0.2989 * textureColor.r + 0.5866 * textureColor.g + 0.1145 * textureColor.b;    float Cr = 0.7132 * (textureColor.r - Y);    float Cb = 0.5647 * (vertColor.b - Y);        float blendValue = smoothstep(thresholdSensitivity, thresholdSensitivity + smoothing, distance(vec2(Cr, Cb), vec2(maskCr, maskCb)));    gl_FragColor = vec4(textureColor.rgb, textureColor.a * blendValue);}

</pre><p></p><p>http://gc-films.com/chromakey.html </p><p></p><pre code_snippet_id="1562456" snippet_file_name="blog_20160125_4_8238969" name="code" class="cpp">double colorclose(int Cb_p,int Cr_p,int Cb_key,int Cr_key,int tola,int tolb) {    /*decides if a color is close to the specified hue*/    double temp = sqrt((Cb_key-Cb_p)*(Cb_key-Cb_p)+(Cr_key-Cr_p)*(Cr_key-Cr_p));    if (temp < tola) {return (0.0);}    if (temp < tolb) {return ((temp-tola)/(tolb-tola));}    return (1.0); } 

http://www.cs.utah.edu/~michael/chroma/

High Quality Chroma Key

这个代码我实现了一下 效果远远达不到要求 专业的摄像机效果好点

头发没法抠出来