在CIFilter中使用來自CIColor的CIImage：獲取空圖像

Question

我正在嘗試使用混合模式創建一個CIFilter（如疊加或乘法）。 相關代碼：

// Let's try a filter here
// Get the data
NSData *imageData = UIImageJPEGRepresentation(image, 0.85);
// Create a CI Image
CIImage *beginImage = [CIImage imageWithData:imageData];
CIImage *overlay = [CIImage imageWithColor:[CIColor colorWithRed:0.7 green:0.75 blue:0.9 alpha:0.75]];
// Create a context
CIContext *context = [CIContext contextWithOptions:nil];
// Create filter
CIFilter *filter = [CIFilter filterWithName:@"CIOverlayBlendMode" 
                                  keysAndValues:@"inputImage", beginImage,
                                                @"inputBackgroundImage", overlay,
                                                nil];

其他過濾器工作正常（如棕褐色調），但是對於需要“inputBackgroundImage”鍵的過濾器，我得到一個空白/空結果......所以我的背景圖像似乎有些問題。

如何通過在圖像上放置純色來使用混合模式濾鏡？

Answer 1

它在主題入門代碼中沒問題，只應該有一個修復。

NSData *imageData = UIImageJPEGRepresentation(image, 0.85);
// Create a CI Image
CIImage *beginImage = [CIImage imageWithData:imageData];
CIImage *overlay = [CIImage imageWithColor:[CIColor colorWithRed:0.7 green:0.75 blue:0.9 alpha:0.75]];

//You should crop the generated image to beginImage size because generated image's size is infinite. I don't know why, but CIOverlayBlendMode isn't tolerant to infinite size
    overlay = [overlay imageByCroppingToRect:CGRectMake(beginImage.extent.origin.x, beginImage.extent.origin.y, beginImage.extent.size.width, beginImage.extent.size.height)];

// Create a context
CIContext *context = [CIContext contextWithOptions:nil];
// Create filter
CIFilter *filter = [CIFilter filterWithName:@"CIOverlayBlendMode" 
                                      keysAndValues:@"inputImage", beginImage,
                                                    @"inputBackgroundImage", overlay,
                                                    nil];

Answer 2

這有效：

//assume beginImage is CIImage you want to tint            
CIImage* outputImage = nil;

//create some blue
CIFilter* blueGenerator = [CIFilter filterWithName:@"CIConstantColorGenerator"];
CIColor* blue = [CIColor colorWithString:@"0.1 0.5 0.8 1.0"];
[blueGenerator setValue:blue forKey:@"inputColor"];
CIImage* blueImage = [blueGenerator valueForKey:@"outputImage"];

//apply a multiply filter
CIFilter* filterm = [CIFilter filterWithName:@"CIMultiplyCompositing"];
[filterm setValue:blueImage forKey:@"inputImage"];
[filterm setValue:beginImage forKey:@"inputBackgroundImage"];
outputImage = [filterm valueForKey:@"outputImage"];