Compare Portable Network Graphics and Bitmap Image formats — understand the key differences and when to use each
Portable Network Graphics
PNG (Portable Network Graphics) is a lossless image format created in 1996 as a patent-free alternative to GIF. PNG uses DEFLATE lossless compression, meaning images retain 100% of their original quality regardless of how many times they're saved. The format supports 8-bit (256 colors) and 24-bit (16.7M colors) color modes, plus a full 8-bit alpha channel for smooth transparency and semi-transparency effects. PNG is the preferred format for screenshots, logos, icons, UI elements, diagrams, and any image requiring sharp edges or transparency. PNG files are typically larger than JPG for photographs but significantly better for graphics with text, solid colors, or transparency. PNG also supports interlacing for progressive loading, gamma correction for cross-platform color consistency, and embedded text metadata. Modern alternatives like WebP and AVIF offer better compression, but PNG remains the gold standard for lossless quality.
Bitmap Image
BMP (Bitmap Image File) is an uncompressed raster image format developed by Microsoft. BMP stores pixel data directly without compression, resulting in very large file sizes but perfect image quality with zero artifacts. The format supports 1-bit (monochrome), 4-bit (16 colors), 8-bit (256 colors), 16-bit, 24-bit, and 32-bit color depths. BMP is primarily used in Windows environments and was historically the default format for Windows Paint. While BMP offers the highest quality preservation, its lack of compression makes it impractical for web use or email. Converting BMP to PNG provides identical visual quality with dramatically smaller file sizes. BMP does not support transparency, animation, or metadata. It remains useful for certain technical applications and as an intermediate format in image processing pipelines.
| Feature | PNG | BMP |
|---|---|---|
| Full Name | Portable Network Graphics | Bitmap Image |
| File Extension | .png | .bmp |
| Category | image | image |
| Free to Convert | ✓ Yes | ✓ Yes |
| Browser Support | ✓ All Browsers | ✓ All Browsers |
| Convert to Each Other | ✓ Yes | ✓ Yes |
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最大文件大小：2GB