I try to make text in image cleaner and clearer before run OCR with tesseract. In this link, they provided a good scripts to do it by ImageMagicK. I wonder is possible to convert this script and function into OpenCV code? For example, the script with arguments like this:
-g -e none -f 15 -o 20
From the explanation:
-g ...................... convert document to grayscale before enhancing
-e .... enhance ......... enhance image brightness before cleaning;
choices are: none, stretch or normalize;
default=none
-f .... filtersize ...... size of filter used to clean background;
integer>0; default=15
-o .... offset .......... offset of filter in percent used to reduce noise;
integer>=0; default=5
How can I do the same in OpenCV code? As I am a newbie in OpenCV, I just only know how to convert to grayscale. Any help would be appreciated.
You have to check ImageMagick documentation to find the exact algorithms used but here is a rough guess:
-g ...................... convert document to grayscale before enhancing
That would be either cv::cvtColor with BGR2GRAY conversion or even better, load directly your image in grayscale with cv::imread(filename,CV_LOAD_IMAGE_GRAYSCALE)
-e .... enhance ......... enhance image brightness before cleaning;
choices are: none, stretch or normalize;
default=none
Since you choosed "none", that would be nothing. Otherwise, use cv::equalizeHist (tutorial).
-f .... filtersize ...... size of filter used to clean background;
integer>0; default=15
-o .... offset .......... offset of filter in percent used to reduce noise;
integer>=0; default=5
My guess for the two latter parameters is cv::adaptiveThreshold with -f corresponding the the blockSize param in OpenCV and -o to the constant C. The actual adaptive thresholding methode (gaussian or mean) is what you need to check in ImageMagick documentation