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I'm trying to threshold this image to get the characters more visible. I've used OTSU threshold but I don't get good results because when I convert the image to gray it is difficult to find a good threshold value. Would you please give me some ideas? Can I threshold an image on another colorspace ? thank you and sorry for my english.

Licence Plate:

first

Gray Licence Plate:

second

Threshold:

third

Roger Rowland
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  • Try doing it in blue space. The text itself is gray initially, so changing to gray might not be the right thing to do. – Jay Bosamiya Jan 30 '15 at 14:08
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    Alternatively, you can convert the license plate into HSV color space. The arrangement of colors in HSV is more structured as in RGB. The segmentation can be done by choosing a range over the H channel. Or if you would like to get a more complex solution then the HV plane can be also used for the segmentation of license plates (blue is a chromatic color, so the S is negligible) – Kornel Jan 30 '15 at 15:40

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