Flip BMP

How to Flip a BMP Image Online

1. Upload Your BMP File: Drag and drop your .bmp file or click "Add Files" to select one. Only the first file you pick is loaded — this editor works on one image at a time, not a batch queue.
2. Choose the Flip Direction: Pick horizontal to mirror left-to-right (the standard "mirror" effect, equivalent to WICBitmapTransformFlipHorizontal in Windows Imaging Component) or vertical to mirror top-to-bottom (a water-reflection effect). Both flips are pure pixel rearrangement — no resampling, no quality loss.
3. Tune Output (Optional): Under Image Compression, choose Quality Preset (Lowest → Highest), Target file size as a percentage, an exact target size in KB/MB, or Image Quality (%). Under Image resolution, keep original or scale by percentage. Set Image bit depth (1, 8, or 16-bit) and Color palette size (2, 4, 8, 16, 32, 64, 128, 256 colors) if you need a palletised BMP.
4. Flip and Download: Click Flip. Processing happens locally in your browser — no sign-up, no watermark.

Why Flip a BMP?

BMP (Windows Bitmap) is Microsoft's native raster format, dating back to the BITMAPCOREHEADER in Windows 2.0 / OS/2 1.x and standardised with the BITMAPINFOHEADER in Windows 3.1x. It is uncompressed by default (optional RLE for indexed images), supports 1, 4, 8, 16, 24, and 32 bits per pixel, and stores scanlines bottom-up unless the height field is negative. That bottom-up convention is exactly why so many BMPs come out vertically inverted from non-Windows toolchains — vertical flip is the fix.

• Correct mirrored scanner output — Many flatbed scanners and document cameras mirror the source when documents are loaded face-down or the optical path uses an internal prism. A horizontal flip restores the original reading direction.
• Fix vertically inverted captures — Embedded systems, microscope cameras, and frame grabbers that write raw .bmp frames frequently emit top-down rows that downstream Windows viewers interpret as bottom-up, producing an upside-down image. A vertical flip realigns it.
• Industrial machine vision — Cognex, Keyence, and Basler line-scan cameras still ship sample BMPs; flipping is part of the calibration step when the sensor is mounted upside-down or the conveyor runs the opposite direction.
• Iron-on transfers and screen printing — Heat-transfer paper and silkscreen positives have to be horizontally mirrored before printing so the design reads correctly once flipped onto the substrate. BMP is still the lingua franca for older Roland and Epson DTG drivers.
• Legacy Windows app assets — Visual Basic 6, MFC dialogs, and ancient game sprite sheets ship as BMP. Designers flipping enemy sprites or button states keep the format intact rather than re-saving as PNG.
• Mirrored variants for design layouts — A symmetrical book cover or product mockup often needs a left-and-right pair from a single source asset.

BMP vs Modern Alternatives — Format Comparison

Compression and Quality Quick Guide

Frequently Asked Questions

Does flipping a BMP lose any quality?

No. Flipping is a pure pixel rearrangement — every pixel is preserved at its full original bit depth. Microsoft's own IWICBitmapFlipRotator describes the operation as a coordinate transform along an axis, with no resampling involved. Compression and quality settings only matter if you choose to recompress the output.

Why does my BMP open upside-down in some viewers but right-side-up in others?

BMP scanlines are stored bottom-up by default; the format also allows top-down ordering by writing a negative biHeight in the header. Tools that ignore the sign assume bottom-up and render top-down BMPs inverted. Apply a vertical flip and re-save to normalise the orientation.

Should I flip horizontally or vertically for an iron-on transfer?

Horizontally. Heat-transfer paper, sublimation transfers, and most screen-printing positives need a left-to-right mirror so the design reads correctly once the paper is flipped onto fabric. Vertical flip is for upside-down captures, not transfers.

Will the output also be a BMP, or do I have to keep the format?

Output stays as .bmp here. If you'd rather move to a smaller modern format after flipping, run BMP to PNG for lossless or BMP to JPG for photographic content — typical 24-bit 1080p shrinks from ~6 MB to ~1–3 MB (PNG) or ~200–500 KB (JPG).

Can I flip a 1-bit (black-and-white) or indexed BMP without breaking the palette?

Yes. The flip operation works on the pixel grid; it doesn't touch the colour table or palette indices. A 1-bit fax-style BMP, an 8-bit indexed sprite sheet, or a 256-colour Windows icon all flip cleanly and remain in the same bit depth unless you change it under Image bit depth.

Does this also work for .dib files or BMPs without the .bmp extension?

Files genuinely in the BMP/DIB container will work if you rename them to .bmp first. The container is detected by the BM magic bytes at offset 0, not by the extension. Truly legacy .dib device-independent bitmaps with the older BITMAPCOREHEADER are also accepted.

Can I flip and crop or rotate in the same step?

Not in this single tool, but the workflow is fast: flip here, then run Crop BMP or Rotate BMP on the result. Each step is lossless on a pure BMP, so chaining them doesn't degrade the image.

Why is my flipped 32-bit BMP showing a black instead of a transparent background?

32-bit BMPs technically support an alpha channel via BI_BITFIELDS, but many legacy Windows viewers ignore it and render the alpha as opaque black. The flip itself preserves the alpha bytes — the issue is the viewer. Re-save as BMP to PNG if you need reliable transparency across modern apps.

Can I flip multiple BMP files in batch?

Not on this page — the editor loads one image at a time. Flip it, save, then + Start New for the next file, choosing the same flip direction and compression settings each time. It's manual, but there's no limit on how many files you work through this way.