以下代码适用于没有 alpha 通道的图像:
CGImageRef c = [[UIImage imageNamed:@"100_3077"] CGImage];
size_t bitsPerPixel = CGImageGetBitsPerPixel(c);
size_t bitsPerComponent = CGImageGetBitsPerComponent(c);
size_t width = CGImageGetWidth(c);
size_t height = CGImageGetHeight(c);
CGImageAlphaInfo a = CGImageGetAlphaInfo(c);
NSAssert(bitsPerPixel == 32 && bitsPerComponent == 8 && a == kCGImageAlphaNoneSkipLast, @"unsupported image type supplied");
CGContextRef targetImage = CGBitmapContextCreate(NULL, width, height, 8, 1 * CGImageGetWidth(c), CGColorSpaceCreateDeviceGray(), kCGImageAlphaNone);
UInt32 *sourceData = (UInt32*)[((__bridge_transfer NSData*) CGDataProviderCopyData(CGImageGetDataProvider(c))) bytes];
UInt32 *sourceDataPtr;
UInt8 *targetData = CGBitmapContextGetData(targetImage);
UInt8 r,g,b;
uint offset;
for (uint y = 0; y < height; y++)
{
for (uint x = 0; x < width; x++)
{
offset = y * width + x;
if (offset+2 < width * height)
{
sourceDataPtr = &sourceData[y * width + x];
r = sourceDataPtr[0+0];
g = sourceDataPtr[0+1];
b = sourceDataPtr[0+2];
targetData[y * width + x] = (r+g+b) / 3;
}
}
}
CGImageRef newImageRef = CGBitmapContextCreateImage(targetImage);
UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
CGContextRelease(targetImage);
CGImageRelease(newImageRef);
使用此代码,我将 rgb 图像转换为灰度图像:
希望这可以帮助