图片压 & 缩上传

壹: 压& 缩 の区别

  • 压是 “压” 文件体积变小，但是像素数不变，长宽尺寸不变，那么质量可能下降.
  • 缩是 “缩” 文件的尺寸变小，也就是像素数减少。长宽尺寸变小，文件体积同样会减小.

贰: 如何使用

  • 给UIImage 建一个分类UIImage+Resize
    在分类里面可以指定
interface UIImage(ResizeCategory)

#pragma mark - -------- 三种缩图 ---------
/** 矩阵缩图片 */
-(UIImage*)resizedImageToSize:(CGSize)dstSize;
/** 上下文画布缩图片 */
- (UIImage*)imageByScalingAndCroppingForSize:(CGSize)targetSize;
/** 等比缩放本图片大小 */
- (UIImage *)compressImage:(UIImage *)image newWidth:(CGFloat)newImageWidth;

#pragma mark - --------- 一种压图 --------
/** 压图片质量 (与 compressImage: newWidth:配合使用的) */
- (NSData *)zipImageWithImage:(CGFloat)newImageMaxSize;

/** 压图片质量 (与 compressImage: newWidth:配合使用的)*/
- (UIImage*)resizedImageToFitInSize:(CGSize)boundingSize scaleIfSmaller:(BOOL)scale;

/** 圆角图*/
- (UIImage *)cutCircleImage ;


//
//  UIImage+Resize.m
//
//  Created by 逯帅 on 17/7/4.
//  Copyright © 2017年 逯帅. All rights reserved.
//


#import "UIImage+Resize.h"

@implementation UIImage (ResizeCategory)

#pragma mark - -------- 三种缩图 ---------

- (UIImage*)resizedImageToSize:(CGSize)dstSize
{
    
    CGImageRef imgRef = self.CGImage;
    // the below values are regardless of orientation : for UIImages from Camera, width>height (landscape)
    CGSize  srcSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef)); // not equivalent to self.size (which is dependant on the imageOrientation)!
    
    /* Don't resize if we already meet the required destination size. */
    if (CGSizeEqualToSize(srcSize, dstSize)) {
        return self;
    }
    
    CGFloat scaleRatio = dstSize.width / srcSize.width;
    UIImageOrientation orient = self.imageOrientation;
    CGAffineTransform transform = CGAffineTransformIdentity;
    switch(orient) {
            
        case UIImageOrientationUp: //EXIF = 1
            transform = CGAffineTransformIdentity;
            break;
            
        case UIImageOrientationUpMirrored: //EXIF = 2
            transform = CGAffineTransformMakeTranslation(srcSize.width, 0.0);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            break;
            
        case UIImageOrientationDown: //EXIF = 3
            transform = CGAffineTransformMakeTranslation(srcSize.width, srcSize.height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;
            
        case UIImageOrientationDownMirrored: //EXIF = 4
            transform = CGAffineTransformMakeTranslation(0.0, srcSize.height);
            transform = CGAffineTransformScale(transform, 1.0, -1.0);
            break;
            
        case UIImageOrientationLeftMirrored: //EXIF = 5
            dstSize = CGSizeMake(dstSize.height, dstSize.width);
            transform = CGAffineTransformMakeTranslation(srcSize.height, srcSize.width);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI_2);
            break;  
            
        case UIImageOrientationLeft: //EXIF = 6  
            dstSize = CGSizeMake(dstSize.height, dstSize.width);
            transform = CGAffineTransformMakeTranslation(0.0, srcSize.width);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI_2);
            break;  
            
        case UIImageOrientationRightMirrored: //EXIF = 7  
            dstSize = CGSizeMake(dstSize.height, dstSize.width);
            transform = CGAffineTransformMakeScale(-1.0, 1.0);
            transform = CGAffineTransformRotate(transform, M_PI_2);
            break;  
            
        case UIImageOrientationRight: //EXIF = 8  
            dstSize = CGSizeMake(dstSize.height, dstSize.width);
            transform = CGAffineTransformMakeTranslation(srcSize.height, 0.0);
            transform = CGAffineTransformRotate(transform, M_PI_2);
            break;  
            
        default:  
            [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];  
            
    }  
    
    // The actual resize: draw the image on a new context, applying a transform matrix
    UIGraphicsBeginImageContextWithOptions(dstSize, NO, self.scale);
    
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {
        CGContextScaleCTM(context, -scaleRatio, scaleRatio);
        CGContextTranslateCTM(context, -srcSize.height, 0);
    } else {  
        CGContextScaleCTM(context, scaleRatio, -scaleRatio);
        CGContextTranslateCTM(context, 0, -srcSize.height);
    }
    
    CGContextConcatCTM(context, transform);
    
    // we use srcSize (and not dstSize) as the size to specify is in user space (and we use the CTM to apply a scaleRatio)
    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, srcSize.width, srcSize.height), imgRef);
    UIImage* resizedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return resizedImage;
}

- (UIImage*)imageByScalingAndCroppingForSize:(CGSize)targetSize
{
    UIImage *sourceImage = self;
    UIImage *newImage = nil;
    CGSize imageSize = sourceImage.size;
    CGFloat width = imageSize.width;
    CGFloat height = imageSize.height;
    CGFloat targetWidth = targetSize.width;
    CGFloat targetHeight = targetSize.height;
    CGFloat scaleFactor = 0.0;
    CGFloat scaledWidth = targetWidth;
    CGFloat scaledHeight = targetHeight;
    CGPoint thumbnailPoint = CGPointMake(0.0,0.0);
    
    if (CGSizeEqualToSize(imageSize, targetSize) == NO)
    {
        CGFloat widthFactor = targetWidth / width;
        CGFloat heightFactor = targetHeight / height;
        
        if (widthFactor > heightFactor)
            scaleFactor = widthFactor; // scale to fit height
        else
            scaleFactor = heightFactor; // scale to fit width
        scaledWidth= width * scaleFactor;
        scaledHeight = height * scaleFactor;
        
        // center the image
        if (widthFactor > heightFactor)
        {
            thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
        }
        else if (widthFactor < heightFactor)
        {
            thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
        }
    }
    
    UIGraphicsBeginImageContext(targetSize); // this will crop
    
    CGRect thumbnailRect = CGRectZero;
    thumbnailRect.origin = thumbnailPoint;
    thumbnailRect.size.width= scaledWidth;
    thumbnailRect.size.height = scaledHeight;
    
    [sourceImage drawInRect:thumbnailRect];
    
    newImage = UIGraphicsGetImageFromCurrentImageContext();
    if(newImage == nil)
        LSLog(@"could not scale image");
    
    //pop the context to get back to the default
    UIGraphicsEndImageContext();
    return newImage;
}

- (UIImage *)compressImage:(UIImage *)image newWidth:(CGFloat)newImageWidth
{
    if (!image) return nil;
    float imageWidth = image.size.width;
    float imageHeight = image.size.height;
    float width = newImageWidth;
    float height = image.size.height/(image.size.width/width);
    
    float widthScale = imageWidth /width;
    float heightScale = imageHeight /height;
    
    // 创建一个bitmap的context
    // 并把它设置成为当前正在使用的context
    UIGraphicsBeginImageContext(CGSizeMake(width, height));
    
    if (widthScale > heightScale) {
        [image drawInRect:CGRectMake(0, 0, imageWidth /heightScale , height)];
    }
    else {
        [image drawInRect:CGRectMake(0, 0, width , imageHeight /widthScale)];
    }
    
    // 从当前context中创建一个改变大小后的图片
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    // 使当前的context出堆栈
    UIGraphicsEndImageContext();
    
    return newImage;
    
}

#pragma mark - --------- 一种压图 --------
/**
 压图片质量
 
 @param image image
 @param newImageMaxSize 压之后图片允许的最大`KB
 @return Data
 */
- (NSData *)zipImageWithImage:(CGFloat)newImageMaxSize
{
    if (!self) {
        return nil;
    }
    CGFloat maxFileSize = newImageMaxSize * 1024;
    CGFloat compression = 0.9f;
    NSData *compressedData = UIImageJPEGRepresentation(self, compression);
    while ([compressedData length] > maxFileSize) {
        compression *= 0.9;
        compressedData = UIImageJPEGRepresentation([self compressImage:self newWidth:self.size.width*compression], compression);
    }
    return compressedData;
}

- (UIImage*)resizedImageToFitInSize:(CGSize)boundingSize scaleIfSmaller:(BOOL)scale
{
    // get the image size (independant of imageOrientation)
    CGImageRef imgRef = self.CGImage;
    CGSize srcSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef)); // not equivalent to self.size (which depends on the imageOrientation)!

    // adjust boundingSize to make it independant on imageOrientation too for farther computations
    UIImageOrientation orient = self.imageOrientation;  
    switch (orient) {
        case UIImageOrientationLeft:
        case UIImageOrientationRight:
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRightMirrored:
            boundingSize = CGSizeMake(boundingSize.height, boundingSize.width);
            break;
        default:
            // NOP
            break;
    }

    
    // Compute the target CGRect in order to keep aspect-ratio
    CGSize dstSize;
    
    if ( !scale && (srcSize.width < boundingSize.width) && (srcSize.height < boundingSize.height) ) {
        //aLog(@"Image is smaller, and we asked not to scale it in this case (scaleIfSmaller:NO)");
        dstSize = srcSize; // no resize (we could directly return 'self' here, but we draw the image anyway to take image orientation into account)
    } else {        
        CGFloat wRatio = boundingSize.width / srcSize.width;
        CGFloat hRatio = boundingSize.height / srcSize.height;
        
        if (wRatio < hRatio) {
            //aLog(@"Width imposed, Height scaled ; ratio = %f",wRatio);
            dstSize = CGSizeMake(boundingSize.width, floorf(srcSize.height * wRatio));
        } else {
            //aLog(@"Height imposed, Width scaled ; ratio = %f",hRatio);
            dstSize = CGSizeMake(floorf(srcSize.width * hRatio), boundingSize.height);
        }
    }
        
    return [self resizedImageToSize:dstSize];
}

/** 设置圆形图片(放到分类中使用) */
- (UIImage *)cutCircleImage {
    UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0);
    // 获取上下文
    CGContextRef ctr = UIGraphicsGetCurrentContext();
    // 设置圆形
    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
    CGContextAddEllipseInRect(ctr, rect);
    // 裁剪
    CGContextClip(ctr);
    // 将图片画上去
    [self drawInRect:rect];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}




@end

叁: 写在后面

上图附带了切圆角图的一个方法

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