从照片库加载图像

Question

1. 如何从照片库加载图像并将其显示在 imageView 中？
2. 如何将图像更改为黑白？

Answer 1

如果你想从照片库加载图像，你必须使用 UIImagePickerController 类。 参考此链接

Answer 2

要将图像形式 UIImagePickerController 转换为黑白，您可以使用以下代码：

UIImage *originalImage = [info objectForKey:UIImagePickerControllerOriginalImage]; // this image we get from UIImagePickerController

CGColorSpaceRef colorSapce = CGColorSpaceCreateDeviceGray();
CGContextRef context = CGBitmapContextCreate(nil, originalImage.size.width, originalImage.size.height, 8, originalImage.size.width, colorSapce, kCGImageAlphaNone);
CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
CGContextSetShouldAntialias(context, NO);
CGContextDrawImage(context, CGRectMake(0, 0, originalImage.size.width, originalImage.size.height), [originalImage CGImage]);

CGImageRef bwImage = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(colorSapce);

UIImage *resultImage = [UIImage imageWithCGImage:bwImage]; // This is result B/W image.
CGImageRelease(bwImage);