围绕着脸部周围添加一个白色阴影渐变
1 CIContext *context = [CIContext contextWithOptions:nil]; 2 UIImage *baby = [UIImage imageNamed:@"baby.jpg"]; 3 CIImage *myImage = [CIImage imageWithCGImage:baby.CGImage]; 4 CIDetector *detector = [CIDetector detectorOfType:CIDetectorTypeFace context:context options:@{CIDetectorAccuracy:CIDetectorAccuracyHigh}]; 5 NSArray *features = [detector featuresInImage:myImage]; 6 CIFaceFeature *faceFeature = [features firstObject]; 7 CGFloat centerX = faceFeature.bounds.origin.x+faceFeature.bounds.size.width / 2.0; 8 CGFloat centerY = faceFeature.bounds.origin.y+faceFeature.bounds.size.height / 2.0; 9 CGFloat radius = MIN(faceFeature.bounds.size.width,faceFeature.bounds.size.height) / 1.5;10 CIFilter *radialGradient = [CIFilter filterWithName:@"CIRadialGradient"keysAndValues:11 @"inputRadius0", @(baby.size.width*2/3),12 @"inputRadius1", @(radius + 10.0f),13 @"inputColor0", [CIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0],14 @"inputColor1", [CIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:0.0],15 kCIInputCenterKey, [CIVector vectorWithX:centerX Y:centerY],nil];16 CIFilter *compositing = [CIFilter filterWithName:@"CISourceOverCompositing" keysAndValues:17 kCIInputImageKey,radialGradient.outputImage,18 kCIInputBackgroundImageKey,myImage,nil];19 CGImageRef cgImage = [context createCGImage:compositing.outputImage fromRect:CGRectMake(0, 0, baby.size.width, baby.size.height)];20 UIImage *maskImage2 = [UIImage imageWithCGImage:cgImage];1 CIContext *context = [CIContext contextWithOptions:nil];2 UIImage *baby = [UIImage imageNamed:@"baby.jpg"];3 CIImage *myImage = [CIImage imageWithCGImage:baby.CGImage];4 CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];5 [filter setValue:myImage forKey:kCIInputImageKey];6 [filter setValue:@20 forKey:kCIInputRadiusKey];从一个单色（如绿色或灰色）创建一个线性渐变，一幅从上倒下变化，另一幅从下到上渐变。然后把它们两个合成一张图像
1 CIFilter *gradientfilter = [CIFilter filterWithName:@"CILinearGradient"]; 2 [gradientfilter setValue:[CIVector vectorWithX:0 Y:0.75*baby.size.height] forKey:@"inputPoint0"]; 3 [gradientfilter setValue:[CIColor colorWithRed:0 green:1 blue:0 alpha:1] forKey:@"inputColor0"]; 4 [gradientfilter setValue:[CIVector vectorWithX:0 Y:0.5 *baby.size.height] forKey:@"inputPoint1"]; 5 [gradientfilter setValue:[CIColor colorWithRed:0 green:1 blue:0 alpha:0] forKey:@"inputColor1"]; 6 7 CIFilter *gradientfilter2 = [CIFilter filterWithName:@"CILinearGradient"]; 8 [gradientfilter2 setValue:[CIVector vectorWithX:0 Y:0.25*baby.size.height] forKey:@"inputPoint0"]; 9 [gradientfilter2 setValue:[CIColor colorWithRed:0 green:1 blue:0 alpha:1] forKey:@"inputColor0"];10 [gradientfilter2 setValue:[CIVector vectorWithX:0 Y:0.5 *baby.size.height] forKey:@"inputPoint1"];11 [gradientfilter2 setValue:[CIColor colorWithRed:0 green:1 blue:0 alpha:0] forKey:@"inputColor1"];12 13 CIFilter *compositingFilter = [CIFilter filterWithName:@"CIAdditionCompositing"];14 [compositingFilter setValue:gradientfilter.outputImage forKey:kCIInputImageKey];15 [compositingFilter setValue:gradientfilter2.outputImage forKey:kCIInputBackgroundImageKey];然后将模糊图像 原图 跟遮罩图像合成在一起。移轴效果比较合适处理建筑物照片人像效果不太好。
1 CIFilter *blendFilter = [CIFilter filterWithName:@"CIBlendWithMask"];2 [blendFilter setValue:blurFilter.outputImage forKey:kCIInputImageKey];3 [blendFilter setValue:myImage forKey:kCIInputBackgroundImageKey];4 [blendFilter setValue:compositingFilter.outputImage forKey:kCIInputMaskImageKey];Core Image的自动强图片效果，会分析图像的直方图，图像属性，脸部区域，然后通过一组滤镜来改善图片效果。
下面这些滤镜可以修正照片中的大部分问题：
| Filter | Purpose |
|---|---|
| CIRedEyeCorrection | Repairs red/amber/white eye due to camera flash |
| CIFaceBalance | Adjusts the color of a face to give pleasing skin tones |
| CIVibrance | Increases the saturation of an image without distorting the skin tones |
| CIToneCurve | Adjusts image contrast |
| CIHighlightShadowAdjust | Adjusts shadow details |
自动增强API仅有2个方法:autoAdjustmentFilters 和 autoAdjustmentFiltersWithOptions: . 多数情况下，我们使用带参数的方法。
CIRedEyeCorrection和CIFaceBalance滤镜，提供图像方向可以使Core Image 更精确的定位到脸的位置。kCIImageAutoAdjustEnhance设置为false）kCIImageAutoAdjustRedEye设置为false）通过autoAdjustmentFiltersWithOptions我们会得到一个包含图像增强的所有的滤镜的数组。依次调用它们处理图像。
1 CIContext *context = [CIContext contextWithOptions:nil];2 UIImage *baby = [UIImage imageNamed:@"1.jpg"];3 CIImage *myImage = [CIImage imageWithCGImage:baby.CGImage];4 NSArray *adjustments = [myImage autoAdjustmentFilters];5 for (CIFilter *filter in adjustments) {6 [filter setValue:myImage forKey:kCIInputImageKey];7 myImage = filter.outputImage;8 }左图就是自动增强之后的效果。
1 CIFilter *filter = [CIFilter filterWithName:@"CIColorMatrix" keysAndValues:2 kCIInputImageKey, myImage,3 @"inputRVector", [CIVector vectorWithX: -1 Y:0 Z:0],4 @"inputGVector", [CIVector vectorWithX:0 Y:-1 Z:0 ],5 @"inputBVector", [CIVector vectorWithX: 0 Y:0 Z:-1],6 @"inputBiasVector", [CIVector vectorWithX:1 Y:1 Z:1],nil];我们可以删除一幅图像中指定的颜色，然后填充一个背景。类似好莱坞大片的背景合成。
要实现上面图片的效果有下面几个步骤
CICOlorCube 滤镜删除图像中通过矩阵变换过的颜色。CISourceOverCompositing 合成图片。一个color cube是一个3D颜色查找表（lookup table）。Core Image 滤镜 CIColorCube 使用色值作为输入，并应用一个查找表到这些色值。CIColorCube从图像中删除所有的绿色。就是要把图中的把绿色的alpha值设置为0.0（透明）。
“绿色”包括一定范围内的颜色。最直接的处理方式是把图像的色值从RGBA转为HSV。HSV把颜色描述在圆柱坐标系内的点。
要删除绿色，你需要定义围绕中心点的最小和最大的角度。之后，对于任何的绿色，将其alpha值设置为0.0。纯绿的相对角度是120o。最小值和最大值要以这个值为中心。
Cube map数据必须预乘alpha，所以创建cube map的最后一步是把RGB值乘以你刚刚计算出的alpha值（如果是绿色，就是0，如果不是就是1.0） 下面是例子代码。
1 CIContext *context = [CIContext contextWithOptions:nil]; 2 UIImage *baby = [UIImage imageNamed:@"2.jpg"]; 3 CIImage *myImage = [CIImage imageWithCGImage:baby.CGImage]; 4 // Allocate memory 5 const unsigned int size = 64; 6 float *cubeData = (float *)malloc (size * size * size * sizeof (float) * 4); 7 float rgb[3], hsv[3], *c = cubeData; 8 9 // Populate cube with a simple gradient going from 0 to 110 for (int z = 0; z < size; z++){11 rgb[2] = ((double)z)/(size-1); // Blue value12 for (int y = 0; y < size; y++){13 rgb[1] = ((double)y)/(size-1); // Green value14 for (int x = 0; x < size; x ++){15 rgb[0] = ((double)x)/(size-1); // Red value16 // Convert RGB to HSV17 // You can find publicly available rgbToHSV functions on the Internet18 RGBtoHSV(rgb[0],rgb[1],rgb[2], &hsv[0],&hsv[1],&hsv[2]);19 20 float alpha = (hsv[0] > 80 && hsv[0] < 130) ? 0.0f:1.0f;21 // Calculate premultiplied alpha values for the cube22 c[0] = rgb[0] * alpha;23 c[1] = rgb[1] * alpha;24 c[2] = rgb[2] * alpha;25 c[3] = alpha;26 c += 4;27 }28 }29 }30 // Create memory with the cube data31 NSData *data = [NSData dataWithBytesNoCopy:cubeData length:(size * size * size * sizeof (float) * 4) freeWhenDone:YES];32 CIFilter *colorCube = [CIFilter filterWithName:@"CIColorCube"];33 [colorCube setValue:@(size) forKey:@"inputCubeDimension"];34 [colorCube setValue:myImage forKey:@"inputImage"];35 [colorCube setValue:data forKey:@"inputCubeData"];36 myImage = colorCube.outputImage;37 38 void RGBtoHSV( float r, float g, float b, float *h, float *s, float *v ){39 float min, max, delta;40 min = MIN( r, MIN(g, b) );41 max = MAX( r, MAX(g, b) );42 *v = max; // v43 delta = max - min;44 if( max != 0 )45 *s = delta / max; // s46 else {47 // r = g = b = 0 // s = 0, v is undefined48 *s = 0;49 *h = -1;50 return;51 }52 if( r == max )53 *h = ( g - b ) / delta; // between yellow & magenta54 else if( g == max )55 *h = 2 + ( b - r ) / delta; // between cyan & yellow56 else57 *h = 4 + ( r - g ) / delta; // between magenta & cyan58 *h *= 60; // degrees59 if( *h < 0 )60 *h += 360;61 }我们可以根据 HSV角度试试删除黄色
float alpha = (hsv[0] > 30 && hsv[0] < 55) ? 0.0f:1.0f;删除指定的颜色后，我们可以填充一个背景图片。
1 UIImage *image2 = [UIImage imageNamed:@"5.png"];2 CIImage *backgroundCIImage = [CIImage imageWithCGImage:image2.CGImage];3 myImage = [[CIFilter filterWithName:@"CISourceOverCompositing" keysAndValues:kCIInputImageKey,myImage,kCIInputBackgroundImageKey,backgroundCIImage,nil] valueForKey:kCIOutputImageKey];4 CGRect extent = [myImage extent];5 CGImageRef cgImage = [context createCGImage:myImage fromRect:extent];Core Image可以对图像进行分析，并找到图片中人脸的位置。Core Image检测出人脸后，可以提供面部特性，比如眼睛和嘴的位置。它还可以跟踪视频中人脸的位置。
下面我们看看如何实现人脸检测。
UIImage *baby = [UIImage imageNamed:@"1.jpg"];CGFloat scale = 320.0/baby.size.width;CIImage *myimage = [CIImage imageWithCGImage:baby.CGImage];CIContext *context = [CIContext contextWithOptions:nil];CIDetector *detector = [CIDetector detectorOfType:CIDetectorTypeFace context:context options:@{CIDetectorAccuracy:CIDetectorAccuracyHigh}];NSArray *features = [detector featuresInImage:myimage];for (CIFaceFeature *faceFeature in features){ CGRect bounds = faceFeature.bounds; bounds.origin.x *= scale; bounds.origin.y *= scale; bounds.size.width *= scale; bounds.size.height *= scale; UIView *faceView = [[UIView alloc] initWithFrame:bounds]; faceView.backgroundColor = [UIColor clearColor]; faceView.layer.borderWidth = 1; faceView.layer.borderColor = [UIColor redColor].CGColor; [self.imageView addSubview:faceView];}此外，我们还可以拿到眼睛跟嘴巴的位置
if (faceFeature.hasLeftEyePosition) NSLog(@"Left eye %@",NSStringFromCGPoint(faceFeature.leftEyePosition));if (faceFeature.hasRightEyePosition) NSLog(@"Right eye %@",NSStringFromCGPoint(faceFeature.rightEyePosition));if (faceFeature.hasMouthPosition) NSLog(@"Mouth %@", NSStringFromCGPoint(faceFeature.mouthPosition));UIImage *baby = [UIImage imageNamed:@"1.jpg"];CIImage *myimage = [CIImage imageWithCGImage:baby.CGImage];CGFloat scale = MAX(baby.size.width, baby.size.height)/60;CIImage *pixlImage =[CIFilter filterWithName:@"CIPixellate" keysAndValues:kCIInputImageKey,myimage,kCIInputScaleKey,@(scale),nil].outputImage;CIImage *maskImage = nil;CIContext *context = [CIContext contextWithOptions:nil];CIDetector *detector = [CIDetector detectorOfType:CIDetectorTypeFace context:context options:@{CIDetectorAccuracy:CIDetectorAccuracyHigh}];NSArray *features = [detector featuresInImage:myimage];for (CIFaceFeature *faceFeature in features){ CGFloat centerX = faceFeature.bounds.origin.x + faceFeature.bounds.size.width / 2.0; CGFloat centerY = faceFeature.bounds.origin.y + faceFeature.bounds.size.height / 2.0; CGFloat radius = MIN(faceFeature.bounds.size.width, faceFeature.bounds.size.height) / 1.5; CIFilter *radialGradient = [CIFilter filterWithName:@"CIRadialGradient" keysAndValues:@"inputRadius0", @(radius),@"inputRadius1", @(radius + 1.0f),@"inputColor0", [CIColor colorWithRed:0.0 green:1.0 blue:0.0 alpha:1.0],@"inputColor1", [CIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:1.0],kCIInputCenterKey, [CIVector vectorWithX:centerX Y:centerY],nil]; CIImage *circleImage = [radialGradient valueForKey:kCIOutputImageKey]; if (nil == maskImage) maskImage = circleImage; else maskImage = [[CIFilter filterWithName:@"CISourceOverCompositing" keysAndValues:kCIInputImageKey, circleImage,kCIInputBackgroundImageKey, maskImage,nil] valueForKey:kCIOutputImageKey]; }}CIImage *resultImage =[CIFilter filterWithName:@"CIBlendWithMask" keysAndValues:kCIInputImageKey,pixlImage,@"inputMaskImage",maskImage,@"inputBackgroundImage",myimage,nil].outputImage;我们在使用 AVFoundation 显示视频的时候，也可以使用 Core Image 进行事实渲染。
#import <UIKit/UIKit.h>#import <GLKit/GLKit.h>#import <AVFoundation/AVFoundation.h>#import <CoreImage/CoreImage.h>@interface ViewController : GLKViewController <AVCaptureVideoDataOutputSampleBufferDelegate> { AVCaptureSession *session; CIContext *coreImageContext;}@property (strong, nonatomic) EAGLContext *context;@end@implementation ViewController@synthesize context = _context;- (void)viewDidLoad{ [super viewDidLoad]; self.context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2]; GLKView *view = (GLKView *)self.view; view.frame = CGRectMake(0, 0, 640, 1136); view.context = self.context; view.drawableDepthFormat = GLKViewDrawableDepthFormat24; coreImageContext = [CIContext contextWithEAGLContext:self.context]; NSError * error; session = [[AVCaptureSession alloc] init]; [session beginConfiguration]; [session setSessionPreset:AVCaptureSessionPreset640x480]; AVCaptureDevice * videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error]; [session addInput:input]; AVCaptureVideoDataOutput * dataOutput = [[AVCaptureVideoDataOutput alloc] init]; [dataOutput setAlwaysDiscardsLateVideoFrames:YES]; [dataOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey]]; [dataOutput setSampleBufferDelegate:self queue:dispatch_get_main_queue()]; [session addOutput:dataOutput]; [session commitConfiguration]; NSArray *array = [[session.outputs objectAtIndex:0] connections]; for (AVCaptureConnection *connection in array){ connection.videoOrientation = AVCaptureVideoOrientationPortrait; } [session startRunning];}-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection { CVPixelBufferRef pixelBuffer = (CVPixelBufferRef)CMSampleBufferGetImageBuffer(sampleBuffer); CIImage *image = [CIImage imageWithCVPixelBuffer:pixelBuffer]; CGRect rect = [image extent]; rect.origin.y = 200; rect.size.width = 640; rect.size.height = (640.0/480.0)*640; CIFilter *filter =[CIFilter filterWithName:@"CISepiaTone"]; [filter setValue:image forKey:kCIInputImageKey]; [filter setValue:@0.8 forKey:kCIInputIntensityKey]; image = filter.outputImage; [coreImageContext drawImage:image inRect:rect fromRect:[image extent] ];}@endQuartz **提供了两种绘制渐变的数据类型，CGShadingRef** 和CGGradientRef 我们都可以始终这两种方式来绘制线性渐变或者辐射渐变。
1 UIGraphicsBeginImageContextWithOptions(CGSizeMake(200, 200),NO ,[UIScreen mainScreen].scale); 2 CGContextRef context = UIGraphicsGetCurrentContext(); 3 size_t locations = 2; 4 CGFloat location[2] ={0.0,1.0}; 5 CGFloat components[8] = {1.0,0.5,0.4,1.0, 6 0.8,0.8,0.3,1.0}; 7 CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 8 CGGradientRef mygradient = CGGradientCreateWithColorComponents(colorSpace, components, location, locations); 9 CGContextDrawLinearGradient (context,mygradient,CGPointMake(0.0, 0.0),CGPointMake(200.0, 200.0), 0);10 UIImage *image = UIGraphicsGetImageFromCurrentImageContext();11 UIGraphicsEndImageContext();//CGContextDrawLinearGradient (context,mygradient,CGPointMake(0.0, 0.0),CGPointMake(200.0, 200.0), 0);CGContextDrawRadialGradient (context,mygradient,CGPointMake(10.0, 10.0),10.0f,CGPointMake(150.0, 150.0),50.0f,kCGGradientDrawsBeforeStartLocation & kCGGradientDrawsAfterEndLocation);CGContextDrawRadialGradient (context,mygradient,CGPointMake(100.0, 100.0),0.0f,CGPointMake(100.0, 100.0),100.0f,kCGGradientDrawsBeforeStartLocation & kCGGradientDrawsAfterEndLocation);size_t locations = 3;CGFloat location[3] ={0.0,0.5,1.0};CGFloat components[12] = {1.0,0.5,0.4,1.0, 0.5,0.5,0.5,1.0, 0.8,0.8,0.3,1.0};我们继承UIButton 然后在 - (void)drawRect: 中 添加渐变效果
- (id)initWithFrame:(CGRect)frame{ self = [super initWithFrame:frame]; if (self) { // Initialization code self.layer.cornerRadius = 8.0f; self.layer.masksToBounds = YES; self.layer.borderWidth = 1.0f; self.layer.borderColor = [UIColor colorWithWhite:0.5f alpha:0.2f].CGColor; } return self;}// Only override drawRect: if you perform custom drawing.// An empty implementation adversely affects performance during animation.- (void)drawRect:(CGRect)rect { CGContextRef ref = UIGraphicsGetCurrentContext(); CGFloat locations[5] = {0.0,0.5,0.5,0.8,1.0}; CFArrayRef colors = (__bridge CFArrayRef) @[(id)[UIColor colorWithWhite:1.0f alpha:0.6f].CGColor, (id)[UIColor colorWithWhite:0.9f alpha:0.3f].CGColor, (id)[UIColor colorWithWhite:0.75f alpha:0.2f].CGColor, (id)[UIColor colorWithWhite:0.4f alpha:0.3f].CGColor, (id)[UIColor colorWithWhite:1.0f alpha:0.2f].CGColor]; CGColorSpaceRef colorSpc = CGColorSpaceCreateDeviceRGB(); CGGradientRef gradient = CGGradientCreateWithColors(colorSpc, colors, locations); CGContextDrawLinearGradient(ref, gradient, CGPointMake(0.5, 0.0), CGPointMake(0.5, rect.size.height), kCGGradientDrawsAfterEndLocation); CGColorSpaceRelease(colorSpc); CGGradientRelease(gradient);}联系客服
