BMP to PDF

BMP is the oldest everyday image format on Windows. Microsoft Paint saved it by default for years, and some scanners, industrial cameras and older programs still produce it. Its weakness is size: a BMP usually stores every single pixel with no compression at all. A full-HD screenshot is about 6 MB, a scanned page at 300 dpi can pass 25 MB. Email and upload forms choke on that. Putting the images in a PDF compresses them and turns a pile of files into one document.

Lossless or smaller?

The choice depends on what the bitmap shows:

• Drawings, diagrams, screenshots, scanned text: choose Lossless. The pixels are stored with PNG-style compression, which shrinks large areas of flat color dramatically, often to a tenth of the BMP size, without changing a single pixel.
• Photos: choose Smaller file. JPEG compression suits photographs and makes the PDF much smaller still, with differences you will hardly see at normal viewing size.

If a photo-like image has transparent areas (rare in BMP), the chosen background color fills them in JPEG mode.

Page size

• A4 or US Letter with margins makes a tidy document for printing; each image is scaled to fit and centred. Auto orientation turns the page sideways for wide images.
• Same as image creates pages exactly the size of each bitmap at screen resolution, useful when the PDF will only be viewed on screen.

Ordering several images

Add as many BMP files as you need. The list shows thumbnails where the browser can display them; drag files into order or use the arrows. The first file becomes page 1.

Typical sources of BMP files

• Drawings and diagrams made in Paint.
• Screenshots saved by older tools or games.
• Output from lab equipment, CNC machines and industrial cameras.
• Scanners set to save “bitmap”.
• Image exports from legacy business software.

After converting

If the PDF is still too large for an email, run it through Compress PDF. To convert a BMP to a regular image file instead, for a website or a document, use the Image Converter. For other formats, see PNG to PDF and JPG to PDF.

Nothing leaves your computer

The bitmaps are decoded by your browser and the PDF is assembled on your device. That keeps drawings, screenshots of internal systems and scans of documents private, and it is faster than uploading 25 MB files.

A worked example: a folder of Paint diagrams

An engineer has twelve wiring diagrams drawn in Paint, each about 3 MB as BMP, 36 MB in total.

1. Add all twelve files and drag them into the order of the manual.
2. Keep Lossless, choose A4 with a small margin and automatic orientation.
3. Create the PDF: a small fraction of the original size, because large flat areas of color compress very well without losing a pixel.
4. Email it to the team; nobody needs an image viewer that understands BMP.

Very large bitmaps

Scans saved as BMP at 600 dpi can be 100 MB per page. The browser has to hold the whole image in memory while converting, so very large files work best on a computer, a few at a time. If a page fails, convert it alone, or first shrink it with the Image Resizer.