Can I save a 2-bit or 3-bit BMP?

[davyike]

I'm building a webserver for an e-ink display that supports 2 or 3-bit grayscale BMP images. Is there any way I can output images like this?

I'm saving 4-bit images as below but the micropython display code can't handle them well.

img.SaveAsBmp(ms, new BmpEncoder()
{
    SupportTransparency = false,
    BitsPerPixel = BmpBitsPerPixel.Pixel4,
});

[brianpopow]

We dont support encoding 2- or 3-Bit bitmaps, because in the specifications those bit depth are not mentioned.

For example:

• Microsoft Windows Bitmap File Format
• OS/2 Bitmap File Format
• Microsoft, Types of Bitmaps, note in the intro to bitmap types 2 bit palette is mentioned, but in the Graphics File Formats section it's not.
• Comprehensive List of all Bitmap types: Here 2 bit per pixels is mentioned as "questional" and that it was legal on Windows CE.

I dont think we should add support for 3 bit bitmaps, since I cant find mentions for those anywhere, but there can be made an argument for adding 2 bit per pixel bitmaps. @JimBobSquarePants: what is your opinion on adding support for 2 bit per pixel bitmaps?

[davyike]

I managed to find a solution to my problem - by using the Arduino library rather than micropython, they have functions that can display a PNG. So I'm now just rendering a PNG from ImageSharp. That said - if this is a small change, it could be handy to others in the future.

Thank you for your response.

[JimBobSquarePants]

@brianpopow The first link you have from the MS docs explicitly lists the bit depths which excludes 2 bit however since it appears from the last link that browsers can display bitmaps of that depth so there must be support out there. If it's not difficult I would say we add it.

[JimBobSquarePants]

Now possible via #2220 Thanks @brianpopow