Prepare complex image for OCR

Question

I want to recognize digits from a credit card. To make things worse, the source image is not guaranteed to be of high quality. The OCR is to be realized through a neural net

Answer 1

in my implementation i tried to use the code from here:http://rnd.azoft.com/algorithm-identifying-barely-legible-embossed-text-image/ results are better but not enough... i find it hard to find the right params for texture cards.

(void)processingByStrokesMethod:(cv::Mat)src dst:(cv::Mat*)dst { 
cv::Mat tmp;  
cv::GaussianBlur(src, tmp, cv::Size(3,3), 2.0);                    // gaussian blur  
tmp = cv::abs(src - tmp);                                          // matrix of differences between source image and blur iamge  

//Binarization:  
cv::threshold(tmp, tmp, 0, 255, CV_THRESH_BINARY | CV_THRESH_OTSU);  

//Using method of strokes:  
int Wout = 12;  
int Win = Wout/2;  
int startXY = Win;  
int endY = src.rows - Win;  
int endX = src.cols - Win;  

for (int j = startXY; j < endY; j++) {  
    for (int i = startXY; i < endX; i++) {  
        //Only edge pixels:  
        if (tmp.at(j,i) == 255)  
        {  
            //Calculating maxP and minP within Win-region:  
            unsigned char minP = src.at(j,i);  
            unsigned char maxP = src.at(j,i);  
            int offsetInWin = Win/2;  

            for (int m = - offsetInWin; m < offsetInWin; m++) {  
                for (int n = - offsetInWin; n < offsetInWin; n++) {  
                    if (src.at(j+m,i+n) < minP) {  
                        minP = src.at(j+m,i+n);  
                    }else if (src.at(j+m,i+n) > maxP) {  
                        maxP = src.at(j+m,i+n);  
                    }  
                }  
            }  

            //Voiting:  
            unsigned char meanP = lroundf((minP+maxP)/2.0);  

            for (int l = -Win; l < Win; l++) {  
                for (int k = -Win; k < Win; k++) {  
                    if (src.at(j+l,i+k) >= meanP) {  
                        dst->at(j+l,i+k)++;  
                    }  
                }  
            }  
        }  
    }  
}  

///// Normalization of imageOut:  
unsigned char maxValue = dst->at(0,0);  

for (int j = 0; j < dst->rows; j++) {              //finding max value of imageOut  
    for (int i = 0; i < dst->cols; i++) {  
        if (dst->at(j,i) > maxValue)  
            maxValue = dst->at(j,i);  
    }  
}  
float knorm = 255.0 / maxValue;  

for (int j = 0; j < dst->rows; j++) {             //normalization of imageOut  
    for (int i = 0; i < dst->cols; i++) {  
        dst->at(j,i) = lroundf(dst->at(j,i)*knorm);  
    }  
}