UIImage OC扩展

OCExt-UIImage.m

@interface UIImage(Color)

/**
* 给指定的图片染色
*/
- (UIImage *)imageWithOverlayColor:(UIColor *)color;

//根据颜色与矩形区生成一张图片
+ (UIImage *)imageFromColor:(UIColor *)color withRect:(CGRect)rect;

//根据View获得一张图片
+ (UIImage *)imageWithView:(UIView *)view;

//把字符串依据指定的字体属性及大小转换成图片
+ (UIImage *)imageFromString:(NSString *)string attributes:(NSDictionary *)attributes size:(CGSize)size;

@end


@interface UIImage(Cut)

//根据指定矩形区,剪裁图片
- (UIImage *)cutImageWithRect:(CGRect)cutRect;

//在指定大小的绘图区域内,将img2合成到img1上
+ (UIImage *) addImageToImage:(UIImage *)img withImage2:(UIImage *)img2
                      andRect:(CGRect)cropRect withImageSize:(CGSize)size;

//把一张图片缩放到指定大小
- (UIImage *)imageToscaledSize:(CGSize)newSize;

//把一张图片按比例缩放到指定大小
- (UIImage*)scaleToSizeKeepAspect:(CGSize)size;

//把图片按指定比例缩放
- (UIImage *)imageToScale:(CGFloat)scale;

@end


@interface UIImage (AverageColor)

//获得图片的平均色值
- (UIColor *)averageColor;

@end

@interface UIImage(Alpha)

- (UIImage *)imageByApplyingAlpha:(CGFloat) alpha;

@end


//------- Implementation -------

@implementation UIImage (Color)

/**
* 给指定的图片染色
*/
- (UIImage *)imageWithOverlayColor:(UIColor *)color {
    CGRect rect = CGRectMake(0.0f, 0.0f, self.size.width, self.size.height);

//    if (UIGraphicsBeginImageContextWithOptions) {
    CGFloat imageScale = 1.0f;
    if ([self respondsToSelector:@selector(scale)])  // The scale property is new with iOS4.
        imageScale = self.scale;
    UIGraphicsBeginImageContextWithOptions(self.size, NO, imageScale);
//    }
//    else {
//        UIGraphicsBeginImageContext(self.size);
//    }

    [self drawInRect:rect];

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetBlendMode(context, kCGBlendModeSourceIn);

    CGContextSetFillColorWithColor(context, color.CGColor);
    CGContextFillRect(context, rect);

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;
}

//根据颜色与矩形区生成一张图片
+ (UIImage *)imageFromColor:(UIColor *)color withRect:(CGRect)rect {
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

//根据View获得一张图片
+ (UIImage *)imageWithView:(UIView *)view {
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];

    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return img;
}

//把字符串依据指定的字体属性及大小转换成图片
+ (UIImage *)imageFromString:(NSString *)string attributes:(NSDictionary *)attributes size:(CGSize)size {
    UIGraphicsBeginImageContextWithOptions(size, NO, 0);
    [string drawInRect:CGRectMake(0, 0, size.width, size.height) withAttributes:attributes];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;
}

@end


@implementation UIImage (Cut)

//根据指定矩形区,剪裁图片
- (UIImage *)cutImageWithRect:(CGRect)cutRect {
    CGImageRef cutImageRef = CGImageCreateWithImageInRect(self.CGImage, cutRect);
    UIImage *cutImage = [UIImage imageWithCGImage:cutImageRef];
    return cutImage;
}

//在指定大小的绘图区域内,将img2合成到img1上
+ (UIImage *)addImageToImage:(UIImage *)img withImage2:(UIImage *)img2
                     andRect:(CGRect)cropRect withImageSize:(CGSize)size {

    UIGraphicsBeginImageContext(size);

    CGPoint pointImg1 = CGPointMake(0, 0);
    [img drawAtPoint:pointImg1];

    CGPoint pointImg2 = cropRect.origin;
    [img2 drawAtPoint:pointImg2];

    UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return result;

}

//把一张图片缩放到指定大小
- (UIImage *)imageToscaledSize:(CGSize)newSize {
    //UIGraphicsBeginImageContext(newSize);
    // In next line, pass 0.0 to use the current device's pixel scaling factor (and thus account for Retina resolution).
    // Pass 1.0 to force exact pixel size.
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [self drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

//把一张图片按长宽等比例缩放到适应指定大小
- (UIImage *)scaleToSizeKeepAspect:(CGSize)size {
    UIGraphicsBeginImageContext(size);

    CGFloat ws = size.width / self.size.width;
    CGFloat hs = size.height / self.size.height;

    if (ws > hs) {
        ws = hs / ws;
        hs = 1.0;
    } else {
        hs = ws / hs;
        ws = 1.0;
    }

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextTranslateCTM(context, 0.0, size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    CGContextDrawImage(context, CGRectMake(size.width / 2 - (size.width * ws) / 2,
            size.height / 2 - (size.height * hs) / 2, size.width * ws,
            size.height * hs), self.CGImage);

    UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return scaledImage;
}

//把图片按指定比例缩放
- (UIImage *)imageToScale:(CGFloat)scale {
    UIGraphicsBeginImageContextWithOptions(self.size, YES, scale);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
    [self drawInRect:CGRectMake(0, 0, self.size.width, self.size.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

@end


@implementation UIImage (AverageColor)

//获得图片的平均色值
- (UIColor *)averageColor {

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char rgba[4];
    CGContextRef context = CGBitmapContextCreate(rgba, 1, 1, 8, 4, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);

    CGContextDrawImage(context, CGRectMake(0, 0, 1, 1), self.CGImage);
    CGColorSpaceRelease(colorSpace);
    CGContextRelease(context);

    if(rgba[3] > 0) {
        CGFloat alpha = ((CGFloat)rgba[3])/255.0;
        CGFloat multiplier = alpha/255.0;
        return [UIColor colorWithRed:((CGFloat)rgba[0])*multiplier
                               green:((CGFloat)rgba[1])*multiplier
                                blue:((CGFloat)rgba[2])*multiplier
                               alpha:alpha];
    }
    else {
        return [UIColor colorWithRed:((CGFloat)rgba[0])/255.0
                               green:((CGFloat)rgba[1])/255.0
                                blue:((CGFloat)rgba[2])/255.0
                               alpha:((CGFloat)rgba[3])/255.0];
    }
}

@end

@implementation UIImage(Alpha)

//修改图片透明度
- (UIImage *)imageByApplyingAlpha:(CGFloat) alpha {
    UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0f);

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

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

    CGContextSetBlendMode(ctx, kCGBlendModeMultiply);

    CGContextSetAlpha(ctx, alpha);

    CGContextDrawImage(ctx, area, self.CGImage);

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return newImage;
}

@end