iOS开发之图片压缩实现

使用下面两个方法，先按尺寸重绘图片，然后再降低品质上传图片data

#pragma mark 裁剪照片
-(UIImage *)scaleToSize:(UIImage *)image size:(CGSize)size
{
    //创建一个bitmap的context
    //并把他设置成当前的context
    UIGraphicsBeginImageContext(size);
    //绘制图片的大小
    [image drawInRect:CGRectMake(0, 0, size.width, size.height)];
    //从当前context中创建一个改变大小后的图片
    UIImage *endImage=UIGraphicsGetImageFromCurrentImageContext();
   
    UIGraphicsEndImageContext();
    return endImage;
}
- (void)printImageDataLength:(UIImage *)image
{
    for (int i=1; i<= 10; i++) {
        NSData *data = UIImageJPEGRepresentation(image, i * 0.1);
        NSLog(@"JPEGdata.length%.1lf = %d",i * 0.1,data.length);
    }
    NSData *data = UIImagePNGRepresentation(image);
    NSLog(@"PNGdata.length = %d",data.length);
}

UIImage的 + (UIImage *)imageWithCGImage:(CGImageRef)cgImage scale:(CGFloat)scale orientation:(UIImageOrientation)orientation方法