The OCR function works different between two similar images

Question

Ahmad Gad 2022-7-23

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回答： Image Analyst 2022-7-25

Hello there.

I am attaching a quite simple two similar images. They both contain the same text. Why MATLAB recognizes one correctly but not the other?

I am trying this code,

ocrResults = ocr(~im2bw(imread('test1.jpg')),'TextLayout','Block')
ocrResults = ocr(~im2bw(imread('test2.jpg')),'TextLayout','Block')

Best, Ahmad

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Answer 1

Walter Roberson 2022-7-24

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You should not be trusting that im2bw will isolate the text when you have multiple background colors. im2bw chooses the threshold automatically and might well decide to threshold between the two different backgrounds.

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Ahmad Gad 2022-7-25

Thanks Walter for the answer.

I think in this current example, they both work regardless if the im2bw function is included or not. However, does this function has alternative? I want to optimize the code if possible.

Thanks!

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Answer 2

Image Analyst 2022-7-25

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It's stated in the OCR documentation that the OCR is not reliable if the characters have less than 20 lines of data, which yours do not. Use a higher resolution image.