CorelDRAW Help | Straightening bitmaps

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Straightening bitmaps

The Straighten image dialog box lets you correct lens distortions and straighten bitmap images quickly. This feature is useful for straightening photos that were taken or scanned at an angle or contain lens distortions.

Straighten image dialog box

Correcting camera lens distortions

With photos that contain camera lens distortions, it is recommended that you start with correcting the lens distortion. You can correct two types of lens distortions, which make straight lines in photos appear curved: barrel and pincushion. Barrel distortions make photos appear pushed out at the center. Pincushion distortions make photos appear pushed in at the center.

Rotating and previewing

The Straighten image dialog box lets you rotate an image by moving a slider, typing a rotation angle, or using the arrow keys. You can specify a custom rotation angle from -15 to 15 degrees.

You can use the preview window to dynamically preview the adjustments that you are making. If you want to change the orientation of the image before straightening it, you can start by rotating the image 90 degrees clockwise and 90 degrees counterclockwise.

A grid is displayed in the preview window to help you straighten the image. You can make more precise adjustments by controlling the cell size of the grid. To heighten the contrast of the grid against the colors of the image, you can change the grid’s color. You can also hide the grid if you want to preview the final result without the gridlines. In addition, you can zoom in and out, and pan the image in the preview window to evaluate the results.

Cropping

By default, the straightened image is cropped to the cropping area that is displayed in the preview window. The final image has the same aspect ratio as the original image, but it has smaller dimensions. However, you can preserve the original width and height of the image by cropping and resampling the image.

You can also produce an image at an angle by disabling cropping and then using the Crop tool to crop the image in the drawing window.

To straighten an image

1 .

Select an image.

2 .

Click Bitmaps

Straighten image.

If the image has a lens distortion, move the Correct lens distortion slider to the left to correct a barrel distortion or to the right to correct a pincushion distortion.

3 .

Move the Rotate image slider, or type a value between 15 and -15 in the Rotate image box.

4 .

If necessary, move the Grid slider to adjust the size of the grid cells.

5 .

To crop and straighten the image, enable the Crop image check box.

The image is cropped to preserve the aspect ratio of the original image, which means that the final image is smaller than the original image.

If you want to preserve the width and height of the original image, enable the Crop and resample to original size check box. The final image is resampled.


You can also
Change the grid color	Choose a color from the Grid color picker.
Align an image area with a gridline	Using the Pan tool , drag the image until the area is aligned with the gridline. You can use the Pan tool only after you zoom in on the image.
Rotate the image 90 degrees in either direction	Click the Rotate counterclockwise button or the Rotate clockwise button .
Hide or display the grid	Disable or enable the Grid check box.
Adjust the rotation angle by 0.1-degree increments	Click in the Rotate image box, and press the Up arrow or Down arrow key.
Reset the image to its original orientation	Click Reset.
Zoom in or out	Using the Zoom in or Zoom out tool, click in the preview window.
Fit an image in the preview window	Click the Zoom to fit button.
Display an image at its actual size	Click the 100% button.

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