BMP to PNG Converter
Convert BMP images to PNG online while preserving image quality and transparency where supported.
Convert BMP files into widely supported PNG images without changing the original image dimensions unless you choose to resize them.
Drag & Drop your BMP here
or Choose BMP
.bmp, .dib • 1-bit to 32-bit color depths
🔒 100% In-Browser Privacy: Your BMP is processed directly in your browser. Zero bytes or pixel data are uploaded to any external server.
How Online BMP to PNG Conversion Works
How binary DIB parsing, 4-byte stride alignment, orientation correction, and lossless PNG encoding produce pristine graphics.
The parser inspects the BITMAPFILEHEADER and DIB header, calculates 4-byte scanline padding stride, and unpacks indexed palettes or raw RGB bitfields accurately.
Standard bottom-up bitmap scanlines are vertically normalized to prevent upside-down output, while 32-bit alpha masks are mapped into standard RGBA color channels.
The reconstructed pixel raster is rendered into a standard 32-bit Canvas buffer and encoded into a genuine PNG file with verified binary headers.
How to Convert BMP to PNG in 4 Easy Steps
Follow these 4 simple steps to transform uncompressed bitmaps into lossless PNG files.
Drag & drop or select your BMP or DIB file from your computer or phone.
Review the decoded image information, adjust transparency background, or set custom dimensions.
Click Convert to execute client-side raster decoding and lossless PNG bitstream encoding.
Inspect the visual comparison and download your genuine PNG image instantly.
BMP vs PNG: Key Format Differences
Understand the architectural differences between uncompressed bitmaps and modern lossless PNG graphics.
| Feature | BMP (Windows Bitmap) | PNG (Portable Network Graphics) |
|---|---|---|
| Compression Type | Uncompressed raw pixels (BI_RGB) or RLE | Lossless DEFLATE compression (LZ77 + Huffman) |
| File Size Efficiency | Very large due to raw byte allocation per pixel | 50% to 90% smaller with identical visual quality |
| Transparency Support | Non-standard / rarely supported (32-bit BGRA only) | Full 8-bit Alpha Channel (256 levels of smooth opacity) |
| Web Compatibility | Not supported natively in modern web layouts | 100% universal across all browsers, apps, and platforms |
| Best Used For | Legacy Windows desktop applications and raw buffers | Websites, UI icons, graphic assets, screenshots, and print |
Frequently Asked Questions
Everything you need to know about converting BMP bitmap graphics to PNG format.
Upload your BMP or DIB file, review the decoded image dimensions and color depth, configure optional background transparency or custom resizing, click 'Convert to PNG', and download your genuine PNG file.
Yes. ReducerImage provides 100% free BMP to PNG conversion with no sign-ups, no usage caps, and no watermarks.
No. PNG uses lossless compression (DEFLATE). Every pixel color, luminance value, and transparency channel from your BMP is preserved with 100% mathematical fidelity.
BMP files are often much larger because they commonly store pixel data with little or no compression. PNG uses lossless compression, so the result may be smaller or larger depending on the image, though typically 50% to 90% smaller.
Yes. By default, the output PNG retains the exact pixel width and height of the original BMP file unless you choose to scale or resize the dimensions.
Yes. If your source BMP contains usable 32-bit RGBA alpha channel data, it will be preserved as transparent PNG pixels. If no alpha channel exists, the output remains cleanly opaque.
Yes. You can specify custom width and height in pixels with an aspect ratio lock, or select one-click presets (1×, 2×, 0.5×).
In rare cases involving 1-bit monochrome or 4-bit indexed bitmaps containing high-entropy photographic noise, 24-bit/32-bit PNG structures can occasionally be comparable or slightly larger than the raw 1-bit binary data.
Yes. The converter runs smoothly in all mobile browsers (Safari on iOS, Chrome on Android) without needing any app installation.
No. Your BMP is processed directly in your browser using HTML5 Canvas and typed arrays. Zero bytes are uploaded to external servers.
Yes. 24-bit RGB/BGR uncompressed Windows bitmaps are fully supported with accurate 4-byte scanline padding alignment.
Yes. 32-bit BGRA bitmaps and bitfield masks are parsed with full support for 8-bit alpha channels.
Yes. 1-bit, 4-bit, and 8-bit indexed BMP files are decoded by parsing the embedded DIB color table palette and mapping each pixel index to RGBA.
Yes. The decoder detects both standard bottom-up bitmaps (positive height) and top-down bitmaps (negative height), correctly orienting the scanlines in the generated PNG.
This tool performs real binary BMP decoding, pixel array transformation, and real PNG bitstream encoding verified with PNG magic bytes (89 50 4E 47).
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