SDWebImage 加载一些大的图片的时候导致程序崩溃

在  UIImage+MultiFormat这个类里面添加如下压缩方法，

+(UIImage *)compressImageWith:(UIImage *)image

{

    float imageWidth = image.size.width;

    float imageHeight = image.size.height;

    float width = 640;

    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;

    

}

再在上面箭头代码后面对图片进行压缩

+ (UIImage *)sd_imageWithData:(NSData *)data {
    UIImage *image;
    NSString *imageContentType = [NSData sd_contentTypeForImageData:data];
    if ([imageContentType isEqualToString:@"image/gif"]) {
        image = [UIImage sd_animatedGIFWithData:data];
    }
#ifdef SD_WEBP
    else if ([imageContentType isEqualToString:@"image/webp"])
    {
        image = [UIImage sd_imageWithWebPData:data];
    }
#endif
    else {
        image = [[UIImage alloc] initWithData:data];
        
        if (data.length/1024 > 128) {
            image = [self compressImageWith:image];
        }
        UIImageOrientation orientation = [self sd_imageOrientationFromImageData:data];
        if (orientation != UIImageOrientationUp) {
            image = [UIImage imageWithCGImage:image.CGImage
                                        scale:image.scale
                                  orientation:orientation];
        }
    }
    return image;
}

到了这里还需要进行最后一步。就是在SDWebImageDownloaderOperation的connectionDidFinishLoading方法里面的：

UIImage *image = [UIImage sd_imageWithData:self.imageData];

//将等比压缩过的image在赋在转成data赋给self.imageData
NSData *data = UIImageJPEGRepresentation(image, 1);
self.imageData = [NSMutableData dataWithData:data];

   再配合    [[SDImageCache sharedImageCache] setValue:nil forKey:@"memCache"];（图片加载后使用）大功告成，亲测内存基本变化不大，自动释放也来得及。