BMP to PNG Converter: Convert Bitmap to PNG Online

Convert BMP to PNG

BMP files store pixels with no compression (or minimal RLE compression), making them unnecessarily large for nearly every use case. PNG provides lossless compression that reduces file size without losing a single pixel of data. This tool converts BMP to PNG in your browser using the Canvas API.

How It Works

1. Drop or select a BMP file
2. The browser’s native image decoder reads the bitmap pixel data
3. The pixels are drawn to a Canvas element
4. The Canvas exports PNG data via toDataURL('image/png')
5. Download the compressed PNG

Because both BMP (uncompressed) and PNG (lossless) represent pixels exactly, the output is visually and numerically identical to the input. Only the file encoding changes.

Why PNG Over BMP

BMP is one of the simplest image formats: a header followed by raw pixel values. This simplicity comes at the cost of file size. PNG applies DEFLATE compression (the same algorithm used in gzip and zip) combined with pre-compression filters that exploit patterns in adjacent pixels.

The compression ratio depends on image content. PNG’s filters predict each pixel from its neighbors, and the DEFLATE algorithm compresses the prediction residuals. Images with large uniform areas (UI screenshots, diagrams) have highly predictable pixels, so they compress dramatically. Photographs have more entropy per pixel and compress less.

When to Choose PNG Over JPEG for BMP Conversion

Both PNG and JPEG produce much smaller files than BMP, but they serve different purposes:

Choose PNG when

• The image contains text, code, or UI elements where sharpness matters
• You need transparency (JPEG does not support alpha channels)
• The image is a diagram, chart, or line drawing
• You need to round-trip the image through further edits without accumulating compression artifacts
• The image is pixel art where every pixel must be exact

Choose JPEG when

• The source is a photograph or scan of a natural scene
• File size is the primary concern and minor quality loss is acceptable
• The image will be displayed at a size where compression artifacts are not visible
• You are optimizing for web delivery of photographic content

For photographic BMP files, the BMP to JPG converter produces smaller files at the cost of lossy compression.

Where BMP Files Come From

You rarely create BMP files intentionally. They appear in specific contexts:

Windows clipboard

Pasting an image from the clipboard in some Windows applications produces BMP. Screen capture tools with default settings sometimes save BMP.

Legacy software exports

Enterprise applications, particularly in healthcare (DICOM viewers), manufacturing, and GIS, often export BMP because the format requires no compression library.

Retro and embedded systems

Game ROM extractors, firmware image dumps, and vintage computing tools frequently produce BMP output because it is trivial to write: just dump the framebuffer with a header.

Converting these to PNG makes them practical to store, share, and use in modern workflows without sacrificing any image data.

For embedding images directly in HTML or CSS, see the Base64 Encoder. For other format conversions, return to the Image Converter.