BMP encoder lost transparency information

[Poker-sang]

if i load this png, and save it into bmp:

var image = Image.Load(path + "avater_default.png");
await image.SaveAsBmpAsync(path + "a.bmp", new BmpEncoder { SupportTransparency = true });
await image.SaveAsPngAsync(path + "a.png");
return;

The bmp one would lose transparency information while the png wouldn't:

bmp:

png:

Is that a bug?

[Poker-sang]

First of all my problem was not using BmpBitsPerPixel.Bit32, but I didn't realize this before because my image viewer said that my BMP was RGBA32

I realized this when I was debugging the ImageSharp repository and noticed that the latest code from the repository encoded the BMP as 8-bit. Is there a fix for BMP that hasn't been released yet? @JimBobSquarePants

[JimBobSquarePants]

Ah yes.

Main is the current V4 preview builds where I have entirely rewritten the format translation process. You can download them from the nightly feed listed in our readme.

Your input PNG is 8bit so V4 correctly encodes it at the same bit depth by default.