ccmain/api.cpp

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// Threshold the given grey or color image into the tesseract global
// image ready for recognition. Requires thresholds and hi_value
// produced by OtsuThreshold above.
void TessBaseAPI::ThresholdRect(const UINT8* imagedata,
                                int bytes_per_pixel,
                                int bytes_per_line,
                                int left, int top,
                                int width, int height,
                                const int* thresholds,
                                const int* hi_values) {
  IMAGELINE line;
  page_image.create(width, height, 1);
  line.init(width);
  // For each line in the image, fill the IMAGELINE class and put it into the
  // Tesseract global page_image. Note that Tesseract stores images with the
  // bottom at y=0 and 0 is black, so we need 2 kinds of inversion.
  //fmg: unless told otherwise, I'll assume that UNIT8* is == char*


  const UINT8* data = imagedata + top*bytes_per_line + left*bytes_per_pixel;
  for (int y = height - 1 ; y >= 0; --y) {
    const UINT8* pix = data;
    for (int x = 0; x < width; ++x, pix += bytes_per_pixel) {
      line.pixels[x] = 1;
      for (int ch = 0; ch < bytes_per_pixel; ++ch) {
        if (hi_values[ch] >= 0 && (pix[ch] > thresholds[ch]) == (hi_values[ch] == 0)) {
          line.pixels[x] = 0;
          break;
        }//if
      }//for bytes in each pixel
    }//for x
    page_image.put_line(0, y, width, &line, 0);
    data += bytes_per_line;
  }//for y
}//TessBaseAPI::ThresholdRect

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