在c＃中调整图像大小（实际的kb / mb大小） [英] Resize a an image (its actual kb/mb size) in c#`

问题描述

这是我用来调整图像大小的代码（实际的kb / mb大小）

This is the code I am using to resize an image (the actual kb/mb size)

public static System.Drawing.Image ScaleImage(System.Drawing.Image image, int maxHeight)
    {
        var ratio = (double)maxHeight / image.Height;
        var newWidth = (int)(image.Width * ratio);
        var newHeight = (int)(image.Height * ratio);
        var newImage = new Bitmap(newWidth, newHeight);

        using (var g = Graphics.FromImage(newImage))
        {
            g.DrawImage(image, 0, 0, newWidth, newHeight);
        }
        return newImage;
    }

但是当我使用这段代码时，它实际上会使图像大小（kb大小）大于它的大小。虽然物理尺寸（宽x高）较小。

我哪里错了？

But when I use this code, it actually makes the image size(kb size) bigger than what it was. Although the physical size (width x height) is smaller.
Where am I going wrong?

推荐答案

首先要做的就是看根据你的数字：在线上设一个断点：

The first thing to do is look at your numbers: put a breakpoint on the line:

var newImage = new Bitmap(newWidth, newHeight);

并使用调试器来检查newHeight，newWidth和比率

我怀疑它们不会是你所期望的。



您是否认为当前图像中的高度低于maxHeight？





BTW：你怎么知道kb / mb的尺寸更大？您是保存新图像还是比较文件大小？如果是这样，它们是同一类型的文件，还是未压缩的格式？

and use the debugger to examine newHeight, newWidth, and ratio
I suspect that they will not be what you expect.

Have you considered what happens in your current image has a lower height than maxHeight?


BTW: How do you know the kb / mb size is bigger? Are you saving the new image and comparing file sizes? If so, are they the same type of file, and an uncompressed format?

你应该检查原始图像的 PixelFormat 并且调整后的大小相同（例如：位图构造函数（ Int32，Int32，PixelFormat） [ ^ ]）。

You should check that the PixelFormat of the original image and of the resized one are the same (see, for instance: Bitmap Constructor (Int32, Int32, PixelFormat)[^]).

我决定使用我当前的代码。我观察到的是，例如2MB的更大图像被调整为更小的KB尺寸，80KB的更小图像变得更大。



BillWoodruff在评论中说的可能是什么正在这里发生。我不知道是否有一个修复，但现在我会按原样使用它，因为它使得非常大的文件至少要小一点

I decided to use the current code that I have. What I observed is that bigger images for example 2MB gets resized to a smaller KB Size and smaller images of 80KB get bigger.

What BillWoodruff said in a comment is probably what is happening here. I don't know if there is a fix for this but for now i'll use it as is because it makes very big files atleast a little bit smaller

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