iOS UIImage(置灰)转换成灰色

方法一：CGColorSpaceCreateDeviceRGB创建一个颜色空间引用

typedefenum{
ALPHA =0,
BLUE =1,
GREEN =2,
RED =3
} PIXELS;
- (UIImage*)convertToGrayscale:(UIImage*)source {
CGSizesize = [sourcesize];
intwidth = size.width;
intheight = size.height;
// the pixels will be painted to this array
uint32_t*pixels = (uint32_t*)malloc(width * height *sizeof(uint32_t));
// clear the pixels so any transparency is preserved
memset(pixels,0, width * height *sizeof(uint32_t));
//颜色空间DeviceRGB
CGColorSpaceRefcolorSpace =CGColorSpaceCreateDeviceRGB();
// create a context with RGBA pixels
CGContextRefcontext =CGBitmapContextCreate(pixels, width, height,8, width *sizeof(uint32_t), colorSpace,kCGBitmapByteOrder32Little|kCGImageAlphaPremultipliedLast);
// paint the bitmap to our context which will fill in the pixels array
CGContextDrawImage(context,CGRectMake(0,0, width, height), source.CGImage);
for(inty =0; y < height; y++) {
for(intx =0; x < width; x++) {
uint8_t*rgbaPixel = (uint8_t*) &pixels[y * width + x];
// convert to grayscale using recommended method:http://en.wikipedia.org/wiki/Grayscale#Converting_color_to_grayscale
uint32_tgray =0.3* rgbaPixel[RED] +0.59* rgbaPixel[GREEN] +0.11* rgbaPixel[BLUE];
// set the pixels to gray
rgbaPixel[RED] = gray;
rgbaPixel[GREEN] = gray;
rgbaPixel[BLUE] = gray;
}
}
// create a new CGImageRef from our context with the modified pixels
CGImageRefimage =CGBitmapContextCreateImage(context);
// we're done with the context, color space, and pixels
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
free(pixels);
// make a new UIImage to return
UIImage*resultUIImage = [UIImageimageWithCGImage:image];
// we're done with image now too
CGImageRelease(image);
returnresultUIImage;
}

方法二：CGColorSpaceCreateDeviceGray会创建一个设备相关的灰度颜色空间的引用

-(UIImage*)createGrayCopy:(UIImage*)source{
intwidth = source.size.width;
intheight = source.size.height;
CGColorSpaceRefcolorSpace =CGColorSpaceCreateDeviceGray();
CGContextRefcontext =CGBitmapContextCreate(nil,
width,
height,
8,// bits per component
0,
colorSpace,
kCGBitmapByteOrderDefault);
CGColorSpaceRelease(colorSpace);
if(context ==NULL) {
returnnil;
}
CGContextDrawImage(context,
CGRectMake(0,0, width, height), source.CGImage);
UIImage*grayImage = [UIImageimageWithCGImage:CGBitmapContextCreateImage(context)];
CGContextRelease(context);
returngrayImage;
}

原文链接：http://keepmovingxin.com/archives/19