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| Understanding Scanners/Monochrome images and Optical Character Recognition (OCR) | Index | Home |
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When text printed against a colored background is scanned, it is not printed out clearly |
Scanned image of a document with a color background |
If a document is scanned as an ordinary color image, its text will be buried in the colored background and be obscure. |
If the importing image type is set for OCR, TET (text enhanced technology) will automatically operate in monochrome mode. Even if the background is colored, TET will pick up the text, read, and reproduce it clearly. However, in this mode, manual threshold value adjustments cannot be made. |
If OCR is not available or TET is not working well, the following method can be used to enhance the text. |
First, for the importing image type, use the 256-color grayscale instead of the line image. Next, use the nonlinear (gamma) correction feature in image editing software to lower the highlights and midtones. This can be done in Photoshop's Levels dialog box which can be opened by selecting Adjust from the Image menu and clicking Levels. |
The level correction feature lowers the highlight and intermediate gradations |
To adjust the tone curve, raise the contrast. This can be done in Photoshop's Curves dialog box which can be opened by selecting "Curves" under Adjust in the Image menu. |
Adjust the tone curve by raising the contrast slope |
The letters have become clear |
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