BMP to PDF Converter

BMP to PDF: Bringing Bitmap Files Into a Shareable Format

BMP, the Windows bitmap, is an old and simple format. It still turns up in practice: older scanners and their bundled software save BMP by default, Microsoft Paint used to, some industrial and medical devices export screen captures as BMP, and archives from the 1990s and 2000s are full of them. BMP files are typically uncompressed, which makes them huge, and many websites and email systems either reject them or display them poorly. A PDF is the natural container to share, print or archive those images.

This tool takes BMP files (and, if you like, other image types alongside them), places each on its own PDF page, and gives you one downloadable document.

The Size Question Comes First With BMP

The server accepts any single image up to 12 MB. With compressed formats that is generous; with BMP it is the limit you are most likely to hit, because an uncompressed 24-bit bitmap uses about three bytes for every pixel. A rough estimate is width × height × 3 bytes (× 4 for 32-bit files):

If a 300 DPI scan is rejected, either rescan at 150 or 200 DPI, or open the BMP in any editor and save it as PNG (lossless, much smaller) or JPEG before converting. Those formats go through this same tool.

The good news runs the other way too: inside the PDF, the bitmap is not stored raw. The PDF library decodes the BMP with PHP's GD extension and keeps the pixels as compressed, lossless PNG-style data. For scans with a lot of white paper, the PDF is often noticeably smaller than the BMP you uploaded, with no loss of detail.

Server Processing, Briefly Explained

The page you see runs in your browser and only builds the list: thumbnails, the counter, ordering and removal. Pressing Convert Images to PDF sends every BMP and the settings of every card to the newisty.com server. Laravel checks that each file is a genuine image of an allowed type (JPG, JPEG, PNG, GIF, WEBP or BMP) within 12 MB. The server writes temporary copies, builds the document with the tc-lib-pdf library, deletes those copies, and stores the PDF in a temporary folder under a random name. An hourly cleanup removes temporary files older than one hour. There is no account or email step.

Converting a Folder of BMP Scans

1. Sort out file names first. Scanner software often numbers files, for example scan0001.bmp, which keeps them in order and unique. The page skips any file whose name already appears in the list.
2. Press Select Images and select all the BMP files, or drag them onto Drop images here. Large bitmaps can take a moment to preview.
3. Check the order of the cards. Drag a card by its grip handle to move it, or press Remove to drop a page you do not want.
4. Match the paper size to the original documents. If you scanned Letter pages, choose Letter in Default Format; for A4 originals keep A4. Then press Apply defaults to all images.
5. Set any landscape originals to Landscape on their own cards.
6. Press Convert Images to PDF. Uploading several megabytes per bitmap takes longer than with JPEG, so allow time on slow connections.
7. Press Download PDF when it appears.

Getting Scanned Pages to Print at Real Size

With W and H left at 0, a bitmap is scaled to fit inside the page, kept in proportion and centred. A full-page scan with the same shape as the paper will fill the page almost exactly, which is what you want for document scans. A scan that includes extra scanner bed around the paper will look slightly shrunk; crop it first if size accuracy matters.

For smaller items, such as a scanned receipt or card, you may prefer real-world size. Open Advanced options on that card and type the item's width in millimetres into W. The height follows automatically from the bitmap's proportions. Use X and Y / Top to position it, measured in millimetres from the top-left corner of the page.

Note that the DPI box does not convert pixels to physical size in the current version. Automatic placement always scales to the page, so DPI has no visible effect, and the Fit on page checkbox is likewise not read by the server. The same applies to Type, Align, Page Align, Resize, Border, Fit Box, Link, Img Mask, Hidden, Is mask and Alt image. Format, orientation, quality and the X, Y, W and H numbers are the settings that count.

Practical Advice

• Convert 32-bit or very large bitmaps to PNG before uploading; they reach the 12 MB cap quickly.
• Black-and-white line art in BMP converts very efficiently once inside the PDF, so it is a good candidate for this tool as is.
• Keep originals. The PDF is a convenient copy, not a replacement for your archive masters.
• Check the PDF page count against the number of BMP files before deleting anything.

Archiving Old Bitmap Collections

When digitising a box of old BMP scans, work in batches of related pages, such as one letter or one invoice set per PDF, rather than one enormous upload. Smaller batches upload faster, are easier to check page by page, and keep each resulting PDF meaningful on its own. Name each downloaded PDF after its contents straight away, because the converter gives it a random name.

Things to Avoid

• Renaming a TIFF or PCX file to .bmp. The server checks real file contents and will reject it.
• Uploading the same scan twice with the same name; the second copy is skipped silently except for a status message.
• Relying on the PDF for text search. Scanned bitmaps are images; there is no OCR in this tool.
• Sending sensitive scans when your rules forbid uploading them to an external server.

Limitations

12 MB per bitmap, one bitmap per page, no rotation or cropping, no margins control, no password on the output and a random output file name. Very old or unusual BMP variants that GD cannot read will fail. To reverse the process and get BMP images out of a PDF, see the PDF to BMP converter; to combine the scan PDF with other PDFs, use Merge PDF.

Frequently Asked Questions