iOS图片压缩最佳方法和图片其他方法

图片压缩最佳方法和图片其他方法

/**
 压缩图片方法(先压缩质量再压缩尺寸,压缩到指定尺寸以下单位如：1 * 1024 Kb)-最佳方法,只能用对象方法，否则无效.
 
 @param maxLength 压缩到指定质量以下，单位KB
 @return 压缩后的
 */
-(NSData *)compressWithLengthLimit:(NSUInteger)maxLength{
    // Compress by quality
    CGFloat compression = 1;
    NSData *data = UIImageJPEGRepresentation(self, compression);
    //NSLog(@"Before compressing quality, image size = %ld KB",data.length/1024);
    if (data.length < maxLength) return data;
    
    CGFloat max = 1;
    CGFloat min = 0;
    for (int i = 0; i < 6; ++i) {
        compression = (max + min) / 2;
        data = UIImageJPEGRepresentation(self, compression);
        //NSLog(@"Compression = %.1f", compression);
        //NSLog(@"In compressing quality loop, image size = %ld KB", data.length / 1024);
        if (data.length < maxLength * 0.9) {
            min = compression;
        } else if (data.length > maxLength) {
            max = compression;
        } else {
            break;
        }
    }
    //NSLog(@"After compressing quality, image size = %ld KB", data.length / 1024);
    if (data.length < maxLength) return data;
    UIImage *resultImage = [UIImage imageWithData:data];
    // Compress by size
    NSUInteger lastDataLength = 0;
    while (data.length > maxLength && data.length != lastDataLength) {
        lastDataLength = data.length;
        CGFloat ratio = (CGFloat)maxLength / data.length;
        //NSLog(@"Ratio = %.1f", ratio);
        CGSize size = CGSizeMake((NSUInteger)(resultImage.size.width * sqrtf(ratio)),
                                 (NSUInteger)(resultImage.size.height * sqrtf(ratio))); // Use NSUInteger to prevent white blank
        UIGraphicsBeginImageContext(size);
        [resultImage drawInRect:CGRectMake(0, 0, size.width, size.height)];
        resultImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        data = UIImageJPEGRepresentation(resultImage, compression);
        //NSLog(@"In compressing size loop, image size = %ld KB", data.length / 1024);
    }
    //NSLog(@"After compressing size loop, image size = %ld KB", data.length / 1024);
    return data;
}

/**
 图片转成Base64字符串,并压缩到指定内存大小
 
 @param image 图片
 @param maxLength 压缩到指定大小，单位kb
 @return 字符串
 */
-(NSString *)imageToBase64Str:(UIImage *) image  MaxLength:(NSInteger)maxLength{
   
    NSData *data = [self compressWithLengthLimit:maxLength * 1024.0f];
    
    NSLog(@"转Base64压缩后图片大小：%luk",(unsigned long)data.length/1024);
    NSString *encodedImageStr = [data base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];
    
    return encodedImageStr;
    
}

/**
 Base64字符串转图片
 
 @param encodedImageStr Base64字符串转
 @return 图片
 */
+(UIImage *)Base64StrToUIImage:(NSString *)encodedImageStr{
    
    NSData * decodedImageData = [[NSData alloc] initWithBase64EncodedString:encodedImageStr options:(NSDataBase64DecodingIgnoreUnknownCharacters)];
    UIImage * decodedImage = [UIImage imageWithData:decodedImageData];
    
    return decodedImage;
}