iOS 不在线好友头像（UIImage）置灰

#import "ViewController.h"

 

typedef enum {

    ALPHA = 0,

    BLUE = 1,

    GREEN = 2,

    RED = 3

} PIXELS;

 

@interface ViewController ()

 

@end

 

@implementation ViewController

 

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

    UIImage *srcImage = [UIImage imageNamed:@"1.png"];

    UIImage *grayImage1 = [self convertToGrayscale:srcImage];

    UIImage *grayImage2 = [self createGrayCopy:srcImage];

    

    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 20, 320, 150)];

    imageView.image = srcImage;

    imageView.contentMode = UIViewContentModeScaleAspectFit;

    [self.view addSubview:imageView];

    

    UIImageView *imageView1 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 175, 320, 150)];

    imageView1.image = grayImage1;

    imageView1.contentMode = UIViewContentModeScaleAspectFit;

    [self.view addSubview:imageView1];

    

    UIImageView *imageView2 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 330, 320, 150)];

    imageView2.image = grayImage2;

    imageView2.contentMode = UIViewContentModeScaleAspectFit;

    [self.view addSubview:imageView2];

}

  // 方法一：CGColorSpaceCreateDeviceRGB创建一个颜色空间引用

- (UIImage *)convertToGrayscale:(UIImage *)source {

    CGSize size = [source size];

    int width = size.width;

    int height = size.height;

    

    // the pixels will be painted to this array

    uint32_t *pixels = (uint32_t *) malloc(width * height * sizeof(uint32_t));

    

    // clear the pixels so any transparency is preserved

    memset(pixels, 0, width * height * sizeof(uint32_t));

    

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    

    // create a context with RGBA pixels

    CGContextRef context = CGBitmapContextCreate(pixels, width, height, 8, width * sizeof(uint32_t), colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedLast);

    

    // paint the bitmap to our context which will fill in the pixels array

    CGContextDrawImage(context, CGRectMake(0, 0, width, height), source.CGImage);

    

    for(int y = 0; y < height; y++) {

        for(int x = 0; x < width; x++) {

            uint8_t *rgbaPixel = (uint8_t *) &pixels[y * width + x];

            

            // convert to grayscale using recommended method: http://en.wikipedia.org/wiki/Grayscale#Converting_color_to_grayscale

            uint32_t gray = 0.3 * rgbaPixel[RED] + 0.59 * rgbaPixel[GREEN] + 0.11 * rgbaPixel[BLUE];

            

            // set the pixels to gray

            rgbaPixel[RED] = gray;

            rgbaPixel[GREEN] = gray;

            rgbaPixel[BLUE] = gray;

        }

    }

    

    // create a new CGImageRef from our context with the modified pixels

    CGImageRef image = CGBitmapContextCreateImage(context);

    

    // we're done with the context, color space, and pixels

    CGContextRelease(context);

    CGColorSpaceRelease(colorSpace);

    free(pixels);

    

    // make a new UIImage to return

    UIImage *resultUIImage = [UIImage imageWithCGImage:image];

    

    // we're done with image now too

    CGImageRelease(image);

    

    return resultUIImage;

}

 

 

 

 //方法二： CGColorSpaceCreateDeviceGray会创建一个设备相关的灰度颜色空间的引用

- (UIImage *)createGrayCopy:(UIImage *)source{

    int width = source.size.width;

    int height = source.size.height;

    

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();

    

    CGContextRef context = CGBitmapContextCreate (nil,

                                                  width,

                                                  height,

                                                  8,      // bits per component

                                                  0,

                                                  colorSpace,

                                                  kCGBitmapByteOrderDefault);

    

    CGColorSpaceRelease(colorSpace);

    

    if (context == NULL) {

        return nil;

    }

    

    CGContextDrawImage(context,

                       CGRectMake(0, 0, width, height), source.CGImage);

    

    UIImage *grayImage = [UIImage imageWithCGImage:CGBitmapContextCreateImage(context)];

    CGContextRelease(context);

    

    return grayImage;

}

 

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

 

@end