CODEWITHSUNDEEP
javarubyimageocrtext-recognition
Stephen Lam
Stephen Lam

Reputation: 65

Finding bounding box of text within JPG image

My question is similar to this one, but is more specific in scope.

In my card game application, I would like for users to be able to click on words located in a scanned jpeg image. Please see this sample Pokemon trading card.

In this case, the user should be able to hover his mouse over the text "Scratch", upon which a pulsing rectangular border will appear around the text, indicating that it is clickable. The problem is how to detect the border of the text. There will be an array of words KNOWN BEFOREHAND that the user may click on (these will be retrieved from a database on a card-by-card basis). To continue our example, the array in this case will be ["Scratch", "Live Coal"]. Once the user clicks on "Scratch", the application must know via a call-back that "Scratch" was chosen instead of "Live Coal".

I was thinking of using optical character recognition libraries to solve this problem, but the open-source options for this are poor in quality (e.g. GOCR) and/or not well-tested on multiple platforms (e.g. Tesseract). I only care about Windows and Mac compatibility. Am I missing an obvious/simpler solution/algorithm that does not require OCR? I cannot simply hand-code in bounding boxes for each card, as there will be thousands of scanned cards in my database. The user may also upload his own custom card scans with an accompanying array of clickable text.

Text color is not always black. See this panorama of different card and text styles that will be permitted. The black cards have white text, and the third-to-last card (Zekrom) has black text with a white outline.

Solutions in any programming language are appreciated. However, please note that I am looking for open-source algorithms and/or libraries. If there is a solution in Ruby or Java, even better, as my code is primarily in these two languages.

EDIT: I forgot to mention that the order of the words/phrases in the array will be the same as on the card. Thus, the array will be ["Scratch", "Live Coal"] instead of ["Live Coal", "Scratch"]. I am mentioning this because it can potentially simplify the task. Thus, for this example, I can simply look for black pixels (though I have to watch out for the black star in the white circle). However, there will be more difficult cases where there is descriptive text under the attack name in a smaller font (again, see the panorama for examples).

Upvotes: 1

Views: 2835

Answers (2)

TookTheRook
TookTheRook

Reputation: 827

When the cursor is stationary, check if there is a black pixel either underneath or to 4 pixels around the cursor. If it is, check the first three consecutive (because there still might be a non-black pixel between the letters) non-black pixels to the left of the cursor, to the right, to the top and at the bottom. If yes, use these locations to draw a square. You can use OpenCV.

Upvotes: 0

Stas Jaro
Stas Jaro

Reputation: 4885

I would just write a program that allows you to visually draw a bounding box around your text for simplicity but could could do this buy detecting differences in pixel color. Since the text is black you could see where the upper-left most black pixel is without large indents and within the bottom half of the card.

Upvotes: 1

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