自由拉伸一张图片

 *  @param name 图片名字
 *  @param left 左边开始位置比例  值范围0-1
 *  @param top  上边开始位置比例  值范围0-1
 + (UIImage *)resizedImageWithName:(NSString *)name left:(CGFloat)left top:(CGFloat)top
 {
     UIImage *image = [UIImage imageNamed:name];
     return [image stretchableImageWithLeftCapWidth:image.size.width * left topCapHeight:image.size.height * top];
 }

根据颜色和大小获取Image

*  @param color 颜色
*  @param size  大小 
+ (UIImage *)imageWithColor:(UIColor *)color size:(CGSize)size
{
    UIGraphicsBeginImageContext(size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, color.CGColor);
    CGContextFillRect(context, CGRectMake(0, 0, size.width, size.height));
    UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return resultImage;  
 }

根据图片和颜色返回一张加深颜色以后的图片

+ (UIImage *)colorizeImage:(UIImage *)baseImage withColor:(UIColor *)theColor {                   UIGraphicsBeginImageContext(CGSizeMake(baseImage.size.width*2, baseImage.size.height*2));

  CGContextRef ctx = UIGraphicsGetCurrentContext();
  CGRect area = CGRectMake(0, 0, baseImage.size.width * 2, baseImage.size.height * 2);

  CGContextScaleCTM(ctx, 1, -1);
  CGContextTranslateCTM(ctx, 0, -area.size.height);

  CGContextSaveGState(ctx);
  CGContextClipToMask(ctx, area, baseImage.CGImage);

  [theColor set];
  CGContextFillRect(ctx, area);

  CGContextRestoreGState(ctx);

  CGContextSetBlendMode(ctx, kCGBlendModeMultiply);

  CGContextDrawImage(ctx, area, baseImage.CGImage);

  UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

  UIGraphicsEndImageContext();

  return newImage;
}

根据图片返回一张高斯模糊的图片(<Accelerate/Accelerate.h>)

*  @param blur 模糊系数
*  @return 新的图片
- (UIImage *)boxblurImageWithBlur:(CGFloat)blur {
    NSData *imageData = UIImageJPEGRepresentation(self, 1); // convert to jpeg
    UIImage* destImage = [UIImage imageWithData:imageData];
    if (blur < 0.f || blur > 1.f) {
        blur = 0.5f;
    }
    int boxSize = (int)(blur * 40);
    boxSize = boxSize - (boxSize % 2) + 1;

    CGImageRef img = destImage.CGImage;
    vImage_Buffer inBuffer, outBuffer;
    vImage_Error error;
    void *pixelBuffer;

//create vImage_Buffer with data from CGImageRef
    CGDataProviderRef inProvider = CGImageGetDataProvider(img);
    CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);

    inBuffer.width = CGImageGetWidth(img);
    inBuffer.height = CGImageGetHeight(img);
    inBuffer.rowBytes = CGImageGetBytesPerRow(img);
    inBuffer.data = (void*)CFDataGetBytePtr(inBitmapData);

    //create vImage_Buffer for output
    pixelBuffer = malloc(CGImageGetBytesPerRow(img) * CGImageGetHeight(img));

    if(pixelBuffer == NULL)
        NSLog(@"No pixelbuffer");

    outBuffer.data = pixelBuffer;
    outBuffer.width = CGImageGetWidth(img);
    outBuffer.height = CGImageGetHeight(img);
    outBuffer.rowBytes = CGImageGetBytesPerRow(img);

    // Create a third buffer for intermediate processing
    void *pixelBuffer2 = malloc(CGImageGetBytesPerRow(img) * CGImageGetHeight(img));
    vImage_Buffer outBuffer2;
    outBuffer2.data = pixelBuffer2;
    outBuffer2.width = CGImageGetWidth(img);
    outBuffer2.height = CGImageGetHeight(img);
    outBuffer2.rowBytes = CGImageGetBytesPerRow(img);

    //perform convolution
    error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer2, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
    if (error) {
        NSLog(@"error from convolution %ld", error);
    }
    error = vImageBoxConvolve_ARGB8888(&outBuffer2, &inBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
    if (error) {
         NSLog(@"error from convolution %ld", error);
    }
    error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
    if (error) {
        NSLog(@"error from convolution %ld", error);
}

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef ctx = CGBitmapContextCreate(outBuffer.data,
                                         outBuffer.width,
                                         outBuffer.height,
                                         8,
                                         outBuffer.rowBytes,
                                         colorSpace,
                                   (CGBitmapInfo)kCGImageAlphaNoneSkipLast);
    CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
    UIImage *returnImage = [UIImage imageWithCGImage:imageRef];

    //clean up
    CGContextRelease(ctx);
    CGColorSpaceRelease(colorSpace);

    free(pixelBuffer);
    free(pixelBuffer2);
    CFRelease(inBitmapData);

    CGImageRelease(imageRef);

    return returnImage;
}

自由改变Image的大小

*  @param size 目的大小
*  @return 修改后的Image
- (UIImage *)cropImageWithSize:(CGSize)size {
    float scale = self.size.width/self.size.height;
    CGRect rect = CGRectMake(0, 0, 0, 0);
    if (scale > size.width/size.height) {
        rect.origin.x = (self.size.width - self.size.height * size.width/size.height)/2;
        rect.size.width  = self.size.height * size.width/size.height;
        rect.size.height = self.size.height;
    }else {
        rect.origin.y = (self.size.height - self.size.width/size.width * size.height)/2;
        rect.size.width  = self.size.width;
        rect.size.height = self.size.width/size.width * size.height;
    }
    CGImageRef imageRef   = CGImageCreateWithImageInRect(self.CGImage, rect);
    UIImage *croppedImage = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
   return croppedImage;
}

UIView转换UIImage代码

- (UIImage*)captureView:(UIView *)theView {
    CGRect rect = theView.frame;
    if ([theView isKindOfClass:[UIScrollView class]]) {
          rect.size = ((UIScrollView *)theView).contentSize;
    }
 
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [theView.layer renderInContext:context];
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return img;
}

UIScrollView转换UIImage代码

- (UIImage *)captureScrollView:(UIScrollView *)scrollView {
    UIImage* image = nil;
    UIGraphicsBeginImageContext(scrollView.contentSize);
    CGPoint savedContentOffset = scrollView.contentOffset;
    CGRect savedFrame = scrollView.frame;
    scrollView.contentOffset = CGPointZero;
    scrollView.frame = CGRectMake(0, 0, scrollView.contentSize.width, scrollView.contentSize.height);
    
    [scrollView.layer renderInContext:UIGraphicsGetCurrentContext()];
    image = UIGraphicsGetImageFromCurrentImageContext();
    
    scrollView.contentOffset = savedContentOffset;
    scrollView.frame = savedFrame;
    UIGraphicsEndImageContext();

    if (image != nil) {
         return image;
    }
    return nil;
}