BYTETOOLS

Image Perspective Correction

Flatten a photo taken at an angle. Drag the four corners of a whiteboard, document or building and get a straight-on rectangle back.

Drop a skewed photo — a whiteboard, document, poster or buildingProcessed locally in your browser — never uploaded

What is the Image Perspective Correction?

Photograph a whiteboard from the side and the writing comes out as a lopsided trapezium. This tool fixes that geometrically: you mark the four corners of the flat surface in the photo, and it works out the projective transform that maps that quadrilateral back to a rectangle, then redraws every output pixel through it.

  • Solves the full 8-parameter homography from your four corners — not a simple stretch or rotate
  • Draggable corner handles plus typed percentage coordinates for precise work
  • Automatic output sizing from the quad's edge lengths, or your own width and height
  • Choice of bilinear or nearest-neighbour sampling
  • Transparent, white or black fill wherever the corrected rectangle falls outside the photo
  • Runs entirely in the browser — nothing is uploaded

How to use the Image Perspective Correction

  1. 1

    Drop in the photo you want to flatten.

  2. 2

    Drag handles 1 to 4 onto the corners of the flat surface, clockwise from the top-left, or type each corner's X and Y position as a percentage.

  3. 3

    Leave the output size on Auto, or switch to Custom and enter the exact width and height you want.

  4. 4

    Pick bilinear sampling for photos or nearest neighbour for line art, and choose what fills any area outside the original photo.

  5. 5

    Check the flattened preview and click Download PNG.

About the Image Perspective Correction

Photograph a whiteboard from the side and the writing comes out as a lopsided trapezium. This tool fixes that geometrically: you mark the four corners of the flat surface in the photo, and it works out the projective transform that maps that quadrilateral back to a rectangle, then redraws every output pixel through it.

Drag the four numbered handles onto the corners of the surface, or type their positions as percentages if you want them exact. You can let the tool size the result from the quad's own edge lengths, or set the output width and height yourself, and choose whether uncovered corners come back transparent, white or black.

Everything runs in your browser on a canvas element. The photo is never uploaded, never sent to a server and never leaves your device — you can disconnect from the internet and the tool still works.

Frequently asked questions

What is perspective correction in a photo?

It is the geometric undoing of the angle you shot from. A flat rectangle photographed off-axis lands on the sensor as a quadrilateral, and perspective correction maps that quadrilateral back to a rectangle so the surface looks like it was shot straight on.

Why do my corners have to be in clockwise order?

The four handles are matched to the four corners of the output rectangle in a fixed order: top-left, top-right, bottom-right, bottom-left. Placing them out of order tells the tool to map the surface to a flipped or twisted rectangle, which is why the result comes out mirrored or folded.

Will correcting perspective make my document blurry?

Slightly, because every output pixel is interpolated from four source pixels. Bilinear sampling keeps photographs smooth; for scanned line art or screenshots, nearest neighbour keeps the pixel edges hard at the cost of some jaggedness.

Can this straighten a photo of a receipt or a book page?

Yes, as long as the page is genuinely flat in the photo. It corrects the viewing angle, not curvature — a curled receipt or a book page that bends into the spine will still bow after correction because no single flat transform describes it.

What output size should I use?

Auto measures the longest pair of opposite edges of your quad and uses those, which keeps roughly the original detail. Switch to Custom when you need an exact aspect ratio, such as squaring up a photo of a painting for print.

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