c# Bitmap.Save transparancy 不保存为 png

c# Bitmap.Save transparancy doesn#39;t save in png(c# Bitmap.Save transparancy 不保存为 png)

问题描述

我正在尝试将具有透明度的位图类保存为具有透明度的 png 文件.我运气不好.

I'm trying to save a Bitmap class that has transparancy as a png file with transparancy. I'm having no luck.

这就是我要做的

Bitmap ret = new Bitmap(bWidth, bHeight, System.Drawing.Imaging.PixelFormat.Format32bppArgb);

保存

ret.Save(filename, ImageFormat.Png);

我也尝试使用文件流保存文件，但没有任何区别.

I also tried saving the file with a filestream, and that made no difference.

当图像在图片框中时，透明度存在，但当我保存时，我只得到黑色背景.

When the image is in a Picture box the transparancy exists, but when I save i I just get a black background.

我真的不想使用任何 3rd 方代码，他们找到了一种方法，我也想这样做.

I really don't want to use any 3rd party code, they found a way to do it, I'd like to also.

谢谢.

推荐答案

我假设对话框的 FilterIndex 从 0 开始...但它实际上从 1 开始，所以我的图像使用 alpha 透明度保存为 Gif, 并且 gif 不支持 alpha 透明度.所以我的问题实际上出在对话框上.

I assumed that the FilterIndex of a dialog box started at 0...but it actually starts at 1, so my images were being saved as Gifs using alpha transparancy, and gif doesn't support alpha transparency. So my problem was actually with the dialog box.

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