ios-将UIImage转换为8位

codeday· 2019-11-17
本文来自 codeday ,作者 codeday
我希望将UIImage转换为8位.我尝试这样做,但是我不确定是否正确,因为稍后在尝试使用图像处理库leptonica指出它不是8位时,我收到一条消息.谁能告诉我我是否正确执行此操作或执行该操作的代码?

谢谢!

 CGImageRef myCGImage = image.CGImage;
 CFDataRef data = CGDataProviderCopyData(CGImageGetDataProvider(myCGImage));
 const UInt8 *imageData = CFDataGetBytePtr(data);
最佳答案
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);

通过此代码,我将rgb图像转换为灰度图像:

希望这可以帮助