BMP 格式未压缩——一张 1024×768 的截图大小为 2.3 MB。同样的图片，JPG 格式只有 120 KB。当文件大小比格式兼容性更重要时，请将 BMP 转换为 JPG。
或者将图片拖放到这里。
支持JPG, JPEG, PNG, WEBP, SVG, GIF, HEIC, HEIF, BMP, TIFF, HDR, JP2, RAF, PSD, CR3, DNG, APNG, AVIF, AVI, ESP, EXR, J2C, J2K, JXL, PFM, PNM, PPM, PSB, SGI, MPEG, PDF
导入 24 位或 32 位 Windows BMP 文件。基于调色板的（1/4/8 位）BMP 文件在处理过程中也会扩展为真彩色。
BMP格式无需压缩解码——它是原始像素数据。像素直接以90质量送入JPEG DCT编码器。转换速度快，节省大量空间。
典型压缩率：缩小 90%–95%。例如，5 MB 的 BMP 文件可以压缩成 200–300 KB 的 JPG 文件。文件名保留 .jpg 扩展名。
Convert BMP to JPG for better compatibility and optimization
Improved file compatibility and optimized performance
Professional-grade conversion with quality preservation
excellent for photos with advanced JPG encoding
Perfect for photography, web images, social media
Handles uncompressed, large file size, simple format from BMP files
未压缩的 1994 年版本与感知压缩的 1992 年版本
Microsoft Windows bitmap
By default the BMP format is version 4. Use BMP3 and BMP2 to write versions 3 and 2 respectively. Use -define bmp:ignore-filesize to ignore the filesize check.
Joint Photographic Experts Group JFIF format
Note, JPG is a lossy compression. In addition, you cannot create black and white images with JPG nor can you save transparency. Requires jpegsrc.v8c.tar.gz. You can set quality scaling for luminance and chrominance separately (e.g. -quality 90,70). You can optionally define the DCT method, for example to specify the float method, use -define jpeg:dct-method=float. By default we compute optimal Huffman coding tables. Specify -define jpeg:optimize-coding=false to use the default Huffman tables. Two other options include -define jpeg:block-smoothing and -define jpeg:fancy-upsampling. Set the sampling factor with -define jpeg:sampling-factor. You can size the image with jpeg:size, for example -define jpeg:size=128x128. To restrict the maximum file size, use jpeg:extent, for example -define jpeg:extent=400KB. To define one or more custom quantization tables, use -define jpeg:q-table=filename. These values are multiplied by -quality argument divided by 100.0. To avoid reading a particular associated image profile, use -define profile:skip=name (e.g. profile:skip=ICC).
格式历史记录、大小缩减和特殊情况。
