Javascript图像处理—亮度对比度应用案例

var brightnessContrast = function(__src, __brightness, __contrast){
__src || error(arguments.callee, IS_UNDEFINED_OR_NULL/* {line} */);
if(__src.type === "CV_RGBA"){
var sData = __src.data,
width = __src.col,
height = __src.row,
dst = new Mat(height, width, CV_RGBA),
dData = dst.data,
brightness = Math.max(-255, Math.min(255, __brightness || 0)),
contrast = Math.max(-255, Math.min(255, __contrast || 0));

var gray = cvtColor(__src, CV_RGBA2GRAY),
allValue = 0,
gData = gray.data;
var y, x, c;

for(y = height; y--;){
for(x = width; x--;){
allValue += gData[y * width + x];
}
}

var r, g, b, offset, gAverage = (allValue / (height * width)) | 0;

for(y = height; y--;){
for(x = width; x--;){
offset = (y * width + x) * 4;
dData[offset] = sData[offset] + brightness;
dData[offset + 1] = sData[offset + 1] + brightness;
dData[offset + 2] = sData[offset + 2] + brightness;

if(contrast >= 0){
for(c = 3; c--;){
if(dData[offset + c] >= gAverage){
dData[offset + c] = dData[offset + c] + (255 - gAverage) * contrast / 255;
}else{
dData[offset + c] = dData[offset + c] - (gAverage * contrast / 255);
}
}
}else{
dData[offset] = dData[offset] + (dData[offset] - gAverage) * contrast / 255;
dData[offset + 1] = dData[offset + 1] + (dData[offset + 1] - gAverage) * contrast / 255;
dData[offset + 2] = dData[offset + 2] + (dData[offset + 2] - gAverage) * contrast / 255;
}

dData[offset + 3] = 255;
}
}
}else{
error(arguments.callee, UNSPPORT_DATA_TYPE/* {line} */);
}
return dst;
};