前言

在這篇文章中積累CoreImage的相關(guān)知識(shí)，這篇文章會(huì)非常的長(zhǎng)。我從18年的5月份開始琢磨無他相機(jī)及其它美顏相機(jī)的相關(guān)圖像處理技術(shù)，斷斷續(xù)續(xù)的了解了一些，又忘記了一些，為了防止再次遺忘，還是決定記錄下來。圖像處理有很多種方式，比如直接對(duì)原始位圖(Raw Bitmap)計(jì)算，使用Core Grahpics、使用GPUImage等，最終，我選擇了CoreImage，這個(gè)框架在視頻圖像上有更加優(yōu)越的性能表現(xiàn)，這是我決定仔細(xì)學(xué)習(xí)它的關(guān)鍵。

正文

從簡(jiǎn)單的圖層混合模式說起

將A圖片疊加到B圖片上，并將A進(jìn)行灰度處理，且尺寸自定。

對(duì)這樣的需求，使用CoreImage的代碼，實(shí)現(xiàn)方式如下:

UIImage *im = [UIImage imageNamed:@"0"];
    UIImage *d = [UIImage imageNamed:@"1"];
    CIImage *cibImage = [CIImage imageWithCGImage:d.CGImage];
    
    
    UIGraphicsBeginImageContext(d.size);
    [im drawInRect:CGRectMake(0, 0, 240, 180)];
    UIImage *imd = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    CIImage *ciaImage = [CIImage imageWithCGImage:imd.CGImage];
    CIFilter *garyFilter = [CIFilter filterWithName:@"CIColorControls"];
    [garyFilter setValue:@0 forKey:@"inputSaturation"];
    [garyFilter setValue:ciaImage forKey:@"inputImage"];
    CIImage *outputImage = garyFilter.outputImage;
    
//    CIFilter *alpheF = [CIFilter filterWithName:@"CIColorMatrix"];
//    [CIVector vectorWithX:0 Y:0 Z:0.5 W:0];
    
    
    CIFilter *blendFilter = [CIFilter filterWithName:@"CISourceAtopCompositing"];
    [blendFilter setValue:outputImage forKey:@"inputImage"];
    [blendFilter setValue:cibImage forKey:@"inputBackgroundImage"];
    
    CIImage *cic = blendFilter.outputImage;
    
    // 6. Render your output image
    CIContext * context = [CIContext contextWithOptions:nil];
    CGImageRef outputCGImage = [context createCGImage:cic fromRect:[cic extent]];
    UIImage * outputImg = [UIImage imageWithCGImage:outputCGImage];
    CGImageRelease(outputCGImage);
    
    
    UIImage *image = [UIImage imageWithCIImage:cic];

疊加效果如下

image.png

如果A的灰度圖片需要添加一定的透明度，那代碼實(shí)現(xiàn)如下

//    CGFloat weights[] = {
//        0, 0, 0.5, 0,
//        0, 0, 0.5, 0,
//        0, 0, 0.5, 0,
//        0, 0, 0.5, 0
//    };
// 對(duì)灰度圖片做透明度處理
    CIFilter *alpheF = [CIFilter filterWithName:@"CIColorMatrix"];
//    CIVector *alpheV = [CIVector vectorWithValues:weights count:9];
    CIVector *alpheV = [CIVector vectorWithX:0 Y:0 Z:0.5 W:0];
    [alpheF setValue:alpheV forKey:@"inputAVector"];
    [alpheF setValue:outputImage forKey:@"inputImage"];
    CIImage *alpheImage = alpheF.outputImage;

效果如下

image.png

CIVector是什么？

舉個(gè)例子：

// 漸變圖片
    // set up the parameters for the filter
    CIVector *centerVector = [CIVector vectorWithX:150 Y:150];
    CIColor *color0 = [CIColor colorWithRed:0 green:0.5 blue:1.0 alpha:1.0];
    CIColor *color1 = [CIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.0];
    NSNumber *radius = [NSNumber numberWithFloat:100.0];

    // create a CIImage and apply the filter
    CIImage *theCIImage = [[CIImage alloc] init];
    theCIImage = [CIFilter filterWithName:@"CIGaussianGradient" keysAndValues:@"inputCenter", centerVector, @"inputColor0", color0, @"inputColor1", color1, @"inputRadius", radius, nil].outputImage;

    // crop the image using CICrop
    CGRect rect = CGRectMake(0.0, 0.0, 600.0, 600.0);
    theCIImage = [CIFilter filterWithName:@"CICrop" keysAndValues:kCIInputImageKey, theCIImage, @"inputRectangle", rect, nil].outputImage;
    
    
    UIImage *image = [UIImage imageWithCIImage:theCIImage];

這種方式可以創(chuàng)建一個(gè)漸變圖片
效果如下：

image.png

再舉個(gè)圓角的例子代碼如下：

    UIImage *im = [UIImage imageNamed:@"0"];
    CIImage *a8 = [CIImage imageWithCGImage:[UIImage   imageNamed:@"8"].CGImage];
    CIFilter *col = [CIFilter filterWithName:@"CIConstantColorGenerator"];
    CIColor *cicor = [[CIColor alloc] initWithColor:[UIColor clearColor]];
    [col setValue:cicor forKey:@"inputColor"];
    CIImage *colorImage = col.outputImage;
    CIFilter *gard = [CIFilter filterWithName:@"CIRadialGradient"];
// CIVector 
    CIVector *center = [CIVector vectorWithX:im.size.width / 2.0 Y:im.size.height / 2.0];
    [gard setValue:center forKey:@"inputCenter"];
    [gard setValue:@85 forKey:@"inputRadius0"];
    [gard setValue:@100 forKey:@"inputRadius1"];
    CIImage *gardImage = gard.outputImage;
    
    CIFilter *blend = [CIFilter filterWithName:@"CIBlendWithMask"];
    [blend setValue:a8 forKey:@"inputImage"];
    [blend setValue:colorImage forKey:@"inputBackgroundImage"];
    [blend setValue:gardImage forKey:@"inputMaskImage"];
    CGImageRef cgImg = [[CIContext contextWithOptions:nil] createCGImage:blend.outputImage fromRect:a8.extent];
    UIImage *image = [UIImage imageWithCGImage:cgImg];

效果:

原圖

image.png

處理后

image.png

這里有一篇CoreImage介紹

給視頻添加水印

- (CIImage *)imageWithLogo:(UIImage *)originalImage {
    // 疊加商標(biāo)
    CIImage *result = [CIImage imageWithCGImage:originalImage.CGImage];
    UIImage *logoImage = [UIImage imageNamed:@"ai_video_logo"];
    // CGAffineTransformMakeTranslation用來調(diào)整相對(duì)屏幕的位置
    CGFloat h = logoImage.size.height / 667.f * originalImage.size.height;
    CGFloat y = 32.f / 667.f * originalImage.size.height;
    CIImage *logoCi = [[CIImage imageWithCGImage:logoImage.CGImage] imageByApplyingTransform:CGAffineTransformMakeTranslation(36, originalImage.size.height - y - h)];
    CIFilter *logoF = [CIFilter filterWithName:@"CISourceOverCompositing"];
    [logoF setValue:logoCi forKey:@"inputImage"];
    [logoF setValue:result forKey:@"inputBackgroundImage"];
    result = [logoF.outputImage imageByCroppingToRect:result.extent];
    return result;
}