使UIImageView变灰

我正在使用来自AFNetworking库的setImageWithUrl在表格单元格中设置UImageViews，但我需要图像为灰度……我有什么方法可以做到这一点。 我尝试了一些UIImage灰度转换器，但我猜它们不起作用，因为我设置的东西尚未下载。

Answer 1

试试这个方法：

- (UIImage *)convertImageToGrayScale:(UIImage *)image { // Create image rectangle with current image width/height CGRect imageRect = CGRectMake(0, 0, image.size.width, image.size.height); // Grayscale color space CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray(); // Create bitmap content with current image size and grayscale colorspace CGContextRef context = CGBitmapContextCreate(nil, image.size.width, image.size.height, 8, 0, colorSpace, kCGImageAlphaNone); // Draw image into current context, with specified rectangle // using previously defined context (with grayscale colorspace) CGContextDrawImage(context, imageRect, [image CGImage]); // Create bitmap image info from pixel data in current context CGImageRef imageRef = CGBitmapContextCreateImage(context); // Create a new UIImage object UIImage *newImage = [UIImage imageWithCGImage:imageRef]; // Release colorspace, context and bitmap information CGColorSpaceRelease(colorSpace); CGContextRelease(context); CFRelease(imageRef); // Return the new grayscale image return newImage; } 

我在这里找到了它： http ： //mobiledevelopertips.com/graphics/convert-an-image-uiimage-to-grayscale.html

Answer 2

我从上面的@Jesse Gumpo的例子中获取了代码，但这里它是一个接口。

 @implementation UIImage ( Greyscale ) - (UIImage *)greyscaleImage { CIImage * beginImage = [ self CIImage ] ; CIImage * evAdjustedCIImage = nil ; { CIFilter * filter = [ CIFilter filterWithName:@"CIColorControls" keysAndValues:kCIInputImageKey, beginImage , @"inputBrightness", @0.0 , @"inputContrast", @1.1 , @"inputSaturation", @0.0 , nil ] ; evAdjustedCIImage = [ filter outputImage ] ; } CIImage * resultCIImage = nil ; { CIFilter * filter = [ CIFilter filterWithName:@"CIExposureAdjust" keysAndValues:kCIInputImageKey, evAdjustedCIImage , @"inputEV", @0.7 , nil ] ; resultCIImage = [ filter outputImage ] ; } CIContext * context = [ CIContext contextWithOptions:nil ] ; CGImageRef resultCGImage = [ context createCGImage:resultCIImage fromRect:resultCIImage.extent ] ; UIImage * result = [ UIImage imageWithCGImage:resultCGImage ] ; CGImageRelease( resultCGImage ) ; return result; } @end 

现在你可以这样做：

 UIImage * downloadedImage = ... get from AFNetwork results ... ; downloadedImage = [ downloadedImage greyscaleImage ] ; ... use 'downloadedImage' ... 

Answer 3

而不是uiimageView，UIView的子类，给它

 @property (strong, nonatomic) UIImage *image; 

同

 @synthesize image = _image; 

覆盖设定者

 -(void)setImage:(UIImage *)image{ _image = [self makeImageBW:image]; [self setNeedsDisplay]; } - (UIImage *)makeImageBW:(UIImage *)source { CIImage *beginImage = source.CIImage; CIImage *blackAndWhite = [CIFilter filterWithName:@"CIColorControls" keysAndValues:kCIInputImageKey, beginImage, @"inputBrightness", [NSNumber numberWithFloat:0.0], @"inputContrast", [NSNumber numberWithFloat:1.1], @"inputSaturation", [NSNumber numberWithFloat:0.0], nil].outputImage; CIImage *output = [CIFilter filterWithName:@"CIExposureAdjust" keysAndValues:kCIInputImageKey, blackAndWhite, @"inputEV", [NSNumber numberWithFloat:0.7], nil].outputImage; CIContext *context = [CIContext contextWithOptions:nil]; CGImageRef ref = [context createCGImage:output fromRect:output.extent]; UIImage *newImage = [UIImage imageWithCGImage:ref]; CGImageRelease(cgiimage); return newImage; } -(void)drawRect:(CGRect)rect{ [_image drawInRect:rect]; } 

在其他地方，您可以使用NSURLRequest设置图像：

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0),^{ NSData *data = [NSURLConnection sendSynchronousRequest:(NSURLRequest *) returningResponse:nil error:nil]; if (data){ UIImage *image = [UIImage imageWithData:data]; if (image) dispatch_async(dispatch_get_main_queue(),^{ [view setImage:image]; }); } }); 

Answer 4

这个post有点旧，但我在搜索时遇到了它。 在这篇文章中，我已经在Swift中指出了两种不同的方法来创建一个灰度图像，可以在imageView中显示，考虑图像的alpha和比例。

 import CoreImage extension UIImage { /// Applies grayscale with CIColorControls by settings saturation to 0.0. /// - Parameter brightness: Default is 0.0. /// - Parameter contrast: Default is 1.0. /// - Returns: The grayscale image of self if available. func grayscaleImage(brightness: Double = 0.0, contrast: Double = 1.0) -> UIImage? { if let ciImage = CoreImage.CIImage(image: self, options: nil) { let paramsColor: [String : AnyObject] = [ kCIInputBrightnessKey: NSNumber(double: brightness), kCIInputContrastKey: NSNumber(double: contrast), kCIInputSaturationKey: NSNumber(double: 0.0) ] let grayscale = ciImage.imageByApplyingFilter("CIColorControls", withInputParameters: paramsColor) let processedCGImage = CIContext().createCGImage(grayscale, fromRect: grayscale.extent) return UIImage(CGImage: processedCGImage, scale: self.scale, orientation: self.imageOrientation) } return nil } /// Create a grayscale image with alpha channel. Is 5 times faster than grayscaleImage(). /// - Returns: The grayscale image of self if available. func convertToGrayScale() -> UIImage? { // Create image rectangle with current image width/height * scale let pixelSize = CGSize(width: self.size.width * self.scale, height: self.size.height * self.scale) let imageRect = CGRect(origin: CGPointZero, size: pixelSize) // Grayscale color space if let colorSpace: CGColorSpaceRef = CGColorSpaceCreateDeviceGray() { // Create bitmap content with current image size and grayscale colorspace let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.None.rawValue) if let context: CGContextRef = CGBitmapContextCreate(nil, Int(pixelSize.width), Int(pixelSize.height), 8, 0, colorSpace, bitmapInfo.rawValue) { // Draw image into current context, with specified rectangle // using previously defined context (with grayscale colorspace) CGContextDrawImage(context, imageRect, self.CGImage) // Create bitmap image info from pixel data in current context if let imageRef: CGImageRef = CGBitmapContextCreateImage(context) { let bitmapInfoAlphaOnly = CGBitmapInfo(rawValue: CGImageAlphaInfo.Only.rawValue) if let contextAlpha = CGBitmapContextCreate(nil, Int(pixelSize.width), Int(pixelSize.height), 8, 0, nil, bitmapInfoAlphaOnly.rawValue) { CGContextDrawImage(contextAlpha, imageRect, self.CGImage) if let mask: CGImageRef = CGBitmapContextCreateImage(contextAlpha) { // Create a new UIImage object if let newCGImage = CGImageCreateWithMask(imageRef, mask) { // Return the new grayscale image return UIImage(CGImage: newCGImage, scale: self.scale, orientation: self.imageOrientation) } } } } } } // A required variable was unexpected nil return nil } }