This guide helps you to align, crop and enhance bitmap images of any type - mostly ones with text in them.
The steps shown in this guide can also be used to prepare images for Optical Character Recognition systems or better print quality.
Status: WIP
Coarse rotation: if the image is upside down, align it roughly (90° steps):
Image » Transform » Rotate …
Coarse crop: if the image has unneeded areas:
⮱ Crop all unnecessary areas using the crop tool (less RAM & CPU usage):
Shift + C
» select area to keep » then crop with ENTER
Fine rotation: if the image doesn't have lines to align with the grid:
⮱ Open the Layers - Dialog with Ctrl + L
or through Windows » Dockable Dialogs » Layers
and create a new layer:
Mode: Normal
Fill with: transparency
Switches: ✖️ Visible
⮱ Press N
to select the pencil:
Brush: 1x1
(1. Pixel)
Size: 1~20 (according to image resolution - you need to see the line)
Everything else: default
Now you can look for a horizontal & vertical position to draw your orientation lines…
…if you want to align to text margins directly, you can also skip this step - not advised!
You can activate the Grid trough View » Show Grid
Select the Arbitrary Rotation - tool, make a coarse alignment and then adjust the image to the exact angle by manipulating the Angle - value (press TAB after changing the value to update the preview). Then apply the changes with Rotate.
Image » Transform » Arbitrary Rotation…
Fine crop: use the crop tool to select the final area of the image you want to preserve. Then press ENTER
Resizing: if needed, resize your image to fit in it's final destination. To do so, select Image » Scale Image…
and adjust it to your needs.
You can also enlarge the image without resizing its contents:
Image » Canvas size…
I created this guide from my own experiences. If you have something to add I'm really thankful to hear from you.
Documentation - Manuals - Guidelines - Instructions by NA0341 is licensed under CC BY-SA 4.0