IOS: Quartz2D图像处理

//
//  UIImage+Zoom.h
//  SvImageEdit
//
//  Created by  maple on 5/22/13.
//  Copyright (c) 2013 maple. All rights reserved.
//

#import <UIKit/UIKit.h>

enum {
    enSvResizeScale,            // image scaled to fill
    enSvResizeAspectFit,        // image scaled to fit with fixed aspect. remainder is transparent
    enSvResizeAspectFill,       // image scaled to fill with fixed aspect. some portion of content may be cliped
};
typedef NSInteger SvResizeMode;



@interface UIImage (Zoom)

/*
 * @brief resizeImage
 * @param newsize the dimensions（pixel） of the output image
 */
- (UIImage*)resizeImageToSize:(CGSize)newSize resizeMode:(SvResizeMode)resizeMode;

@end

//
//  UIImage+Zoom.m
//  SvImageEdit
//
//  Created by  maple on 5/22/13.
//  Copyright (c) 2013 maple. All rights reserved.
//

#import "UIImage+Zoom.h"

@implementation UIImage (Zoom)

/*
 * @brief resizeImage
 * @param newsize the dimensions（pixel） of the output image
 */
- (UIImage*)resizeImageToSize:(CGSize)newSize resizeMode:(SvResizeMode)resizeMode
{
    CGRect drawRect = [self caculateDrawRect:newSize resizeMode:resizeMode];
    
    UIGraphicsBeginImageContext(newSize);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextClearRect(context, CGRectMake(0, 0, newSize.width, newSize.height));
    
    CGContextSetInterpolationQuality(context, 0.8);
    
    [self drawInRect:drawRect blendMode:kCGBlendModeNormal alpha:1];
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return image;
}

// caculate drawrect respect to specific resize mode
- (CGRect)caculateDrawRect:(CGSize)newSize resizeMode:(SvResizeMode)resizeMode
{
    CGRect drawRect = CGRectMake(0, 0, newSize.width, newSize.height);
    
    CGFloat imageRatio = self.size.width / self.size.height;
    CGFloat newSizeRatio = newSize.width / newSize.height;
    
    switch (resizeMode) {
        case enSvResizeScale:
        {
            // scale to fill
            break;
        }
        case enSvResizeAspectFit:                    // any remain area is white
        {
            CGFloat newHeight = 0;
            CGFloat newWidth = 0;
            if (newSizeRatio >= imageRatio) {        // max height is newSize.height
                newHeight = newSize.height;
                newWidth = newHeight * imageRatio;
            }
            else {
                newWidth = newSize.width;
                newHeight = newWidth / imageRatio;
            }
            
            drawRect.size.width = newWidth;
            drawRect.size.height = newHeight;
            
            drawRect.origin.x = newSize.width / 2 - newWidth / 2;
            drawRect.origin.y = newSize.height / 2 - newHeight / 2;
            
            break;
        }
        case enSvResizeAspectFill:
        {
            CGFloat newHeight = 0;
            CGFloat newWidth = 0;
            if (newSizeRatio >= imageRatio) {        // max height is newSize.height
                newWidth = newSize.width;
                newHeight = newWidth / imageRatio;
            }
            else {
                newHeight = newSize.height;
                newWidth = newHeight * imageRatio;
            }
            
            drawRect.size.width = newWidth;
            drawRect.size.height = newHeight;
            
            drawRect.origin.x = newSize.width / 2 - newWidth / 2;
            drawRect.origin.y = newSize.height / 2 - newHeight / 2;
            
            break;
        }
        default:
            break;
    }
    
    return drawRect;
}

@end

//
//  UIImage+SvImageEdit.m
//  SvImageEdit
//
//  Created by  maple on 5/8/13.
//  Copyright (c) 2013 maple. All rights reserved.
//

#import "UIImage+Crop.h"

@implementation UIImage (SvImageEdit)

/*
 * @brief crop image with path
 */
- (UIImage*)cropImageWithPath:(NSArray*)pointArr
{
    if (pointArr.count == 0) {
        return nil;
    }
    
    CGPoint *points = malloc(sizeof(CGPoint) * pointArr.count);
    for (int i = 0; i < pointArr.count; ++i) {
        points[i] = [[pointArr objectAtIndex:i] CGPointValue];
    }
    
    UIGraphicsBeginImageContext(CGSizeMake(self.size.width * self.scale, self.size.height * self.scale));
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    CGContextBeginPath(context);
    CGContextAddLines(context, points, pointArr.count);
    CGContextClosePath(context);
    CGRect boundsRect = CGContextGetPathBoundingBox(context);
    UIGraphicsEndImageContext();

    UIGraphicsBeginImageContext(boundsRect.size);
    context = UIGraphicsGetCurrentContext();
    CGContextClearRect(context, CGRectMake(0, 0, boundsRect.size.width, boundsRect.size.height));
    
    CGMutablePathRef  path = CGPathCreateMutable();
    CGAffineTransform transform = CGAffineTransformMakeTranslation(-boundsRect.origin.x, -boundsRect.origin.y);
    CGPathAddLines(path, &transform, points, pointArr.count);
    
    CGContextBeginPath(context);
    CGContextAddPath(context, path);    
    CGContextClip(context);
    
    [self drawInRect:CGRectMake(-boundsRect.origin.x, -boundsRect.origin.y, self.size.width * self.scale, self.size.height * self.scale)];
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    
    CGPathRelease(path);
    UIGraphicsEndImageContext();
    
    return image;
}

@end