Question

I am trying to draw some basic graphics primitives(line, rectangle etc.) using GDI+ apis on 4-bit indexed bitmaps. I am using Bitmap() functions for creating the bitmap and loading the bitmaps.

Bitmap myBitmap(100/*width*/,100/*height*/,PixelFormat4bppIndexed/*Pixel format*/);
Graphics graphics(&myBitmap);
SolidBrush brush(Color(255,128,0,0));
graphics.FillRectangle(&brush,0,0,100,100);

But this doesn’t work(No Rectangle created).
What could be the problem? I tried manually using LockBits and modifying the bits manually, it works well, then why it doesn’t work with Graphics gdi+ operations.

Answer 1

Finally I managed to solve my problem. To perform gdi+ operations using Graphics object on 4 bit indexed bitmap, we need to perform following steps.

1. Create 4bpp HBITMAP directly or load image from file using LoadImage.
2. If loading from 4bpp file, then load palette from file in HPALETTE object.
3. Create desktop compatible dc.
4. Select and realize you palette in newly created dc.
5. select HBITMAP in your dc.
6. Create Graphics object using your dc.
7. Perform GDI+ operations on 4bpp indexed.

Though I didnt try with 8bpp but I think similar operations can be performed on 8bpp also.

Hope this help others also.