按大小压缩图像 - iPhone SDK [英] image compression by size - iPhone SDK

问题描述

我想压缩图像(相机/照片库)，然后将其发送到服务器.我知道我可以按高度和宽度压缩，但我只想按大小将图像压缩到固定大小(200 KB)并保持原始高度和宽度.JPEGRepresentation 中的比例因子不代表大小，只代表压缩质量.如何在不使用任何第三方库的情况下实现这一点(压缩到固定大小)?感谢您的帮助.

I would like to compress images (camera/photo library) and then send it to the server. I know I can compress by height and width, but I would like to compress the images by size to a fixed size (200 KB) only and keep the original height and width. The scale factor in JPEGRepresentation does not represent the size and only compression quality. How can I achieve this (compress to a fixed size) without using any third party library? Thanks for any help.

推荐答案

这里有一些示例代码，它们将尝试为您压缩图像，使其不超过最大压缩率或最大文件大小

Heres some example code that will attempt to compress an image for you so that it doesn't exceed either a max compression or maximum file size

CGFloat compression = 0.9f;
CGFloat maxCompression = 0.1f;
int maxFileSize = 250*1024;

NSData *imageData = UIImageJPEGRepresentation(yourImage, compression);

while ([imageData length] > maxFileSize && compression > maxCompression)
{
    compression -= 0.1;
    imageData = UIImageJPEGRepresentation(yourImage, compression);
}

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