如何使用UIImagePNGRepresentation - iOS压缩图像大小

Question

我正在使用UIImagePNGRepresentation来保存图像。结果图像的大小为 30+ KB，这在我的情况下很大。

我尝试使用UIImageJPEGRepresentation，它允许压缩图像，因此图像以 5KB 大小保存

如何使用UIImagePNGRepresentation压缩图像大小？

Answer 1

PNG使用无损压缩，这就是为什么UIImagePNGRepresentation不像UIImageJPEGRepresentation那样接受compressionQuality参数。使用不同的工具，您可能会获得较小的PNG文件，但与JPEG完全不同。

Answer 2

也许这会帮助你：

- (void)resizeImage:(UIImage*)image{
    NSData *finalData = nil;
    NSData *unscaledData = UIImagePNGRepresentation(image);
    if (unscaledData.length > 5000.0f ) {

       //if image size is greater than 5KB dividing its height and width maintaining proportions

        UIImage *scaledImage = [self imageWithImage:image andWidth:image.size.width/2 andHeight:image.size.height/2];
        finalData = UIImagePNGRepresentation(scaledImage);
        if (finalData.length > 5000.0f ) {
            [self resizeImage:scaledImage];
        }
        //scaled image will be your final image
    }
}

调整图像大小

- (UIImage*)imageWithImage:(UIImage*)image andWidth:(CGFloat)width andHeight:(CGFloat)height
{
    UIGraphicsBeginImageContext( CGSizeMake(width, height));
    [image drawInRect:CGRectMake(0,0,width,height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext() ;
    return newImage;
}