JPG to BMP Converter

Why Convert JPG to BMP?

BMP (Bitmap, also known as DIB — Device Independent Bitmap) is one of the oldest and simplest raster image formats, developed by Microsoft for the Windows operating system. BMP stores images in uncompressed form, recording information about each pixel directly to the file. This ensures absolute reproduction accuracy but results in very large files.

Converting JPG to BMP is required in specific situations: when compatibility with legacy Windows software is needed, when working with specialized industrial equipment, or when guaranteed format support by any program is required. Despite its venerable age, BMP remains a useful tool for certain tasks thanks to its simplicity and universal compatibility.

History of the BMP Format

The BMP format was created by Microsoft in 1986 for the Windows 1.0 operating system. This makes it one of the oldest graphics formats still in use today. The main goal was to provide a simple and universal way to store raster images for the Windows graphical interface.

The name BMP comes from the word Bitmap — referring to a raster image. The format is also known as DIB (Device Independent Bitmap), emphasizing its independence from specific output devices.

Evolution of BMP Format

Over the years, the format has gone through several versions:

• BMP version 1 (1986) — basic format for Windows 1.0
• BMP version 2 (1990) — for Windows 3.0 (OS/2 BMP)
• BMP version 3 (1992) — most common version for Windows 3.x
• BMP version 4 (1995) — for Windows 95, added ICC color profile support
• BMP version 5 (1998) — for Windows 98, full ICC profile and alpha channel support

In practice, most BMP files use version 3 (BITMAPINFOHEADER), which provides sufficient functionality with maximum compatibility.

Technical Structure of BMP Format

BMP File Structure

A BMP file consists of several sequential blocks:

1. File Header (BITMAPFILEHEADER) — 14 bytes:

   • Signature "BM" (2 bytes) — format identifier
   • File size in bytes (4 bytes)
   • Reserved fields (4 bytes)
   • Offset to image data start (4 bytes)

2. Information Header (DIB Header) — 40+ bytes:

   • Header size (determines format version)
   • Image width in pixels
   • Image height (can be negative for top-down scanning)
   • Number of color planes (always 1)
   • Color depth (bits per pixel)
   • Compression type
   • Image data size
   • Horizontal and vertical resolution (pixels per meter)
   • Number of colors in palette
   • Number of important colors

3. Color Palette (optional) — for images with 8-bit or lower color depth

4. Image Data — the actual pixels, usually scanned bottom-up

Color Depth in BMP

BMP supports various color depths:

When converting from JPG, a 24-bit BMP is usually created, as JPG uses the same color depth (8 bits per RGB channel).

Compression in BMP

Contrary to popular belief, BMP can use compression:

In practice, the vast majority of BMP files use BI_RGB mode (no compression), which is what makes them so large.

Row Storage Peculiarity

Important technical detail: in BMP, each image row (scanline) must be aligned to a 4-byte boundary. If the image width in bytes is not divisible by 4, additional padding bytes are added. This is a legacy of 32-bit Windows architecture, optimized for data alignment.

For example, for a 24-bit image 10 pixels wide:

• Row data: 10 × 3 bytes = 30 bytes
• Alignment: 30 → 32 bytes (2 bytes added)

JPG vs BMP Format Comparison

When to Use BMP Instead of JPG

BMP has advantages in the following cases:

• Working with legacy Windows software — programs from the 1990s and 2000s
• Industrial equipment — CNC machines, plotters, specialized printers
• Maximum compatibility — file guaranteed to open in any program
• No recompression — avoiding additional quality loss
• Windows system tasks — icons, cursors, desktop wallpapers (historically)

When JPG Is Better Than BMP

JPG remains the best choice for:

• Web publishing — BMP is not supported by modern browsers for practical use
• Photo storage — compact size with acceptable quality
• File transfer — smaller size means faster transfer
• Social media — no platform accepts BMP

JPG to BMP Conversion Process

Conversion Stages

1. JPG Decoding — unpacking compressed JPEG data
2. Inverse DCT — restoring pixel values from frequency coefficients
3. YCbCr→RGB Conversion — converting from JPG color space to RGB
4. BMP Header Creation — forming BITMAPFILEHEADER and BITMAPINFOHEADER
5. Pixel Writing — row-by-row data writing bottom-up with 4-byte alignment

What Is Preserved During Conversion

When converting JPG to BMP: ✅ All pixels of the original image ✅ Dimensions (width and height) ✅ Color reproduction (within 24-bit precision)

What Is NOT Preserved

❌ EXIF metadata (shooting date, camera, geolocation) ❌ ICC color profile ❌ Image rotation information ❌ Data lost during JPG creation (artifacts remain)

File Size: JPG vs BMP

One of the main conversion features is the dramatic file size increase:

Formula for calculating 24-bit BMP size:

Size ≈ (Width × 3 + alignment) × Height + 54 bytes headers

This explains why BMP is almost never used for storing photographs — one shot from a modern camera would take up hundreds of megabytes.

BMP Software Compatibility

Operating Systems

Web Browsers

Browser	BMP in	BMP in CSS
Chrome	✅	✅
Firefox	✅	✅
Safari	✅	✅
Edge	✅	✅
Opera	✅	✅

Technically browsers support BMP, but using it on websites is strongly not recommended due to huge file sizes.

Graphics Editors

BMP is supported by absolutely all graphics programs:

• Microsoft Paint — native format
• Adobe Photoshop — full support
• GIMP — full support
• CorelDRAW — full support
• Affinity Photo — full support
• Paint.NET — full support

This is one of BMP's main advantages — the file is guaranteed to open in any image editing program.

BMP Applications in the Modern World

Industrial Equipment

BMP remains popular in industry:

• CNC machines — engraving and milling equipment
• Laser cutters — for processing raster images
• Plotters — large-format printing
• Embroidery machines — basic models
• Printed circuit boards — creating photo templates

Many of these devices have firmware developed decades ago and support only basic image formats.

Embedded Systems

BMP is often used in embedded systems with limited resources:

• Format simplicity means minimal decoding code
• No complex library required for unpacking
• Predictable memory usage

Game Development (historically)

In the DOS and early Windows era, BMP was the standard format for game graphics:

• Character and object sprites
• Textures for 3D graphics
• Interface elements

Modern game engines use more efficient formats, but BMP can still be found in game modification tools.

BMP Alternatives

PNG — for Most Tasks

PNG offers lossless compression with significantly smaller size:

• Size: 3-10 times smaller than BMP
• Transparency: full alpha channel
• Web compatibility: supported by all browsers
• Metadata: text block support

TIFF — for Professional Tasks

TIFF is suitable for professional tasks:

• Printing: industry standard
• Archiving: long-term storage
• Metadata: full EXIF, IPTC, XMP support

WebP Lossless — for Modern Web

WebP from Google is the optimal choice for web projects:

• Compression: better than PNG
• Support: all modern browsers
• Transparency: full alpha channel

Practical Recommendations

When to Convert JPG to BMP

✅ Do convert if:

• Equipment or software requires specifically BMP
• Guaranteed compatibility with legacy systems is needed
• Working with industrial equipment
• Creating files for embedded systems

❌ Don't convert if:

• Planning to publish on the internet
• File size matters
• Metadata (EXIF) is needed
• PNG is an option

Recommended Settings

When converting JPG to BMP:

• Color depth: 24-bit (True Color) — matches source JPG
• Compression: no compression (BI_RGB) — maximum compatibility
• Scan direction: standard (bottom-up)

BMP Size Optimization

If file size is critical, you can reduce BMP:

• Reduce resolution — fewer pixels = smaller file
• 8-bit palette — 256 colors instead of 16 million (with quality loss)
• RLE compression — for simple images with large areas of single color

Conclusion

Converting JPG to BMP is a specific operation for working with legacy software and specialized equipment. BMP remains a useful format thanks to its simplicity and universal compatibility, but its huge file sizes make it impractical for most modern tasks. For lossless image storage, PNG is better; for professional tasks, TIFF; and for web publishing, WebP. Choose BMP only when truly necessary for compatibility.