以下代码应该能满足您的需求。大部分代码来自于
如何设置UIImage的不透明度/透明度?我只添加了一个alpha值测试,在将像素的颜色转换为黑色之前进行测试。
CGImageRef imageRef = [[UIImage imageNamed:@"testImage"] CGImage];
NSUInteger width = CGImageGetWidth(imageRef);
NSUInteger height = CGImageGetHeight(imageRef);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
UInt8 * m_PixelBuf = malloc(sizeof(UInt8) * height * width * 4);
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;
CGContextRef context = CGBitmapContextCreate(m_PixelBuf, width, height,
bitsPerComponent, bytesPerRow, colorSpace,
kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
CGContextRelease(context);
int length = height * width * 4;
for (int i=0; i<length; i+=4) {
if (m_PixelBuf[i+3] != 0) {
m_PixelBuf[i+3] = 255;
}
}
CGContextRef ctx = CGBitmapContextCreate(m_PixelBuf, width, height,
bitsPerComponent, bytesPerRow, colorSpace,
kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGImageRef newImgRef = CGBitmapContextCreateImage(ctx);
CGColorSpaceRelease(colorSpace);
CGContextRelease(ctx);
free(m_PixelBuf);
UIImage *finalImage = [UIImage imageWithCGImage:newImgRef];
CGImageRelease(newImgRef);
finalImage
现在将包含一张图像,在这张图像上所有不透明度不为0.0的像素都将具有1.0的透明度。
for (int i=0; i
- Halpo