by The Photoshop Perspective Crop tool does two jobs in one drag: it crops to a four-sided region and squares that region into a rectangle. Photograph a page, a whiteboard, a painting or a shop sign at an angle, draw the four corners, press Enter, and you have a straight-on view. It is the fastest perspective tool in Photoshop and the one most people never find, because it lives in a fly-out. Adobe's reference is the crop and straighten page in the Photoshop user guide.
Perspective Crop is a variant of the Crop tool that accepts a quadrilateral instead of a rectangle. Photoshop computes the projective transform that maps the four corners you drew onto a rectangle, applies it to the pixels inside, and discards everything outside. It is the same maths as a four-corner perspective correction, with the crop built in.
Where it is
Press C to select the Crop tool, then hold the mouse on the Crop icon in the toolbar (or press Shift + C) and pick Perspective Crop Tool from the fly-out. The cursor changes to a crop marker with a small grid.
Step 1 — draw the four corners
Click once on each corner of the object, in order around the shape (top-left, top-right, bottom-right, bottom-left, or any consistent order). A marquee with a grid appears. You can also drag a rectangle first and then drag each corner into place; either way, what matters is where the four corners end up.
Zoom in (Ctrl/Cmd + +) and nudge each corner exactly onto the object's corner. The grid inside the marquee is the check: its lines should run parallel to the object's edges and its interior lines should line up with rows of text, tiles or bricks. Show Grid in the options bar toggles it if it is hidden.
Step 2 — set the output size, or don't
In the options bar there are W, H and Resolution fields and a Front Image button. For a normal correction leave them empty: Photoshop keeps the pixel dimensions of the region. Fill them in when you need a specific result, such as a scanned page at 210 × 297 mm at 300 ppi; Photoshop then resamples the region to that size. Front Image copies the size and resolution of the current document into the fields, which is useful when you want the crop to match another open image. Clear empties them.
Step 3 — commit
Press Enter, or click the tick in the options bar. The result is a rectangular image of the object, straight on. Because pixels have been re-projected, it is slightly softer than the original: apply Filter → Sharpen → Unsharp Mask at a low amount (50%, radius 1) if it is a document, or leave it for a painting.
Getting the proportions right
Perspective Crop squares the shape, but it cannot know the real aspect ratio of the object; it infers it from the four points, which works well for mild angles and drifts for steep ones. If a page comes out slightly too wide or too narrow, fix it afterwards with Image → Image Size with Resample on and the chain unlinked, entering the true proportions (A4 is 1 : 1.414, Letter 1 : 1.294). For paintings, measure the real canvas.
Common problems
The result is stretched or skewed. A corner is off the true corner, or the object is not rectangular. Undo, zoom in, re-place the corners. For a curved or non-rectangular subject, use Perspective Warp instead.
"Could not use the perspective crop tool because the selected area is empty." The selected layer has no pixels under the marquee: an empty layer, a mask, or a Smart Object placeholder. Select the layer with the image, or Layer → Flatten Image.
The tool crops but does not straighten. You dragged a rectangle and pressed Enter without moving the corners. It behaves like the normal Crop tool until the corners are placed on a perspective shape.
Everything outside the shape disappears. That is the crop. If you want to keep the surroundings, use the perspective correction tool here or Perspective Warp, which reshape without cropping.
Doing it without Photoshop
The same four-corner straighten-and-crop runs in the browser with the perspective correction tool: drag the corners, export at full resolution, nothing is uploaded. It is the quicker route for one whiteboard photo on a phone.
Related
Photoshop perspective tools overview · Photoshop Perspective Warp · Photoshop perspective grid · Fix perspective in Affinity
Questions
Where is the Perspective Crop tool in Photoshop?
Hidden under the Crop tool in the toolbar. Click and hold the Crop tool icon (or press C, then Shift + C to cycle) and choose Perspective Crop Tool from the fly-out.
What is the difference between Crop and Perspective Crop?
Crop cuts a rectangle. Perspective Crop lets you draw a four-sided shape over something photographed at an angle, and turns that shape into a rectangle as it crops, straightening the object in the same step.
Why does Perspective Crop stretch my image?
Because the four corners you drew are not on the true corners of a rectangular object, or the object is not really rectangular. Zoom in and place each corner exactly; for a non-rectangular subject, use Perspective Warp instead.
How do I keep the original size and resolution?
Leave the W, H and Resolution fields in the options bar empty and Front Image unchecked. Photoshop then keeps the pixel dimensions of the cropped region. Fill them in only if you need a specific output size, for example a scan at 300 ppi A4.
Could not use the Perspective Crop tool because the selected area is empty — what does that mean?
The layer has no pixels inside the crop shape, usually because a layer mask, an empty layer or a Smart Object placeholder is selected. Select the pixel layer that contains the image and try again, or flatten first.