CodesBeautify

BMP to GIF Converter

Reduce a bitmap to a GIF palette of up to 256 colours, chosen by a median cut of the actual image.

BMP file

Drop a file here, paste from the clipboard, or choose one

BMP, processed in this tab

GIF result

The result appears here

Result
Runs locally in your browser

About the BMP to GIF Converter

GIF holds an indexed palette of at most 256 entries, so the millions of colours a 24-bit bitmap can carry have to be boiled down first. This converter builds a histogram of the bitmap, groups the colours into boxes, repeatedly splits the widest box along its longest axis, and averages each final box into one palette entry. That median cut approach keeps the colours the picture actually uses rather than snapping everything to a fixed web palette.

Interface mock-ups, pixel art, logos and charts survive the reduction almost perfectly, because they rarely use more than a few dozen distinct tones. Photographs are a different matter: skies and skin tones show visible banding once they are pinned to 256 entries. Lowering the Colours setting to 64 or 32 shrinks the file further and is often invisible on flat graphics.

GIF supports one bit of transparency, meaning a pixel is either fully visible or fully absent. Keep transparency maps every pixel under 50 percent alpha to the transparent palette slot; switch it off to paint those pixels onto a solid background instead. The GIF to BMP tool walks the same road backwards.

How to use

  1. Select the bitmap you want indexed.
  2. Pick a palette size under Colours: 256 for photos, 32 or 64 for flat artwork.
  3. Untick Keep transparency if the GIF must sit on a solid colour.
  4. Download the GIF once the preview looks right.

Common questions

Why does my photograph look banded as a GIF?
A GIF can hold only 256 distinct colours. Smooth gradients get quantised into visible steps, which is normal for the format.
Can this produce an animated GIF?
No. It writes a single still frame. Animation needs several source images and a frame delay, which is outside what this converter does.
What does the Colours setting really change?
It caps the size of the palette written into the file. Fewer colours mean a smaller GIF and coarser tone steps.
Is the palette the same for every image?
No, it is computed from your bitmap each time, so a picture of a forest gets a green heavy palette and a blueprint gets blues and greys.