スキャン画像の余白を圧縮＆文字を太く＆1024x758にリサイズするプログラム。要OpenCV。変数erodeitを変更すると圧縮度合いが変わります。

compressSpace.cpp

#include <iostream>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>

int main(int argc, char* argv[])
{
	if(argc==1) {
		std::cout << "Usage: compressSpace input_img" << std::endl;
		return 0;
	}
	cv::Mat src_img = cv::imread(argv[1], 0);
	if(src_img.empty()) {
		std::cerr << "Image Load Failed!" << std::endl;
		return -1;
	}
	static const std::string fileName_ext = argv[1];
	static std::string fileName(fileName_ext, 0, fileName_ext.size()-4);
	static const std::string empty_string;
	static std::ostringstream os;
	// border whitening
	int border = (int)(src_img.rows*2.0/100);
	cv::rectangle(src_img, cv::Point(0,0),
		cv::Point(src_img.cols, src_img.rows),
		cv::Scalar::all(255), border, CV_AA);
	cv::Mat dst_img, compRows, compCols;
	// binarize
	cv::Mat bin_img, fg_img, rev_img, char_img, compressed;
	cv::threshold(src_img, bin_img, 0, 255, cv::THRESH_BINARY|cv::THRESH_OTSU);
	cv::bitwise_xor(src_img, cv::Scalar::all(255), rev_img);
	// denoise
	cv::threshold(rev_img, char_img, 0, 255, cv::THRESH_TOZERO|cv::THRESH_OTSU);
	// dilate
	cv::pyrUp(char_img, rev_img);
	cv::dilate(rev_img, char_img, cv::Mat(), cv::Point(-1,-1), 1);
	cv::bitwise_xor(char_img, cv::Scalar::all(255), rev_img);
	// cv::dilate(rev_img, rev_img, cv::Mat(), cv::Point(-1,-1), 1);
	cv::resize(rev_img, char_img, cv::Size(), 0.5, 0.5, cv::INTER_LINEAR);
	int erodeit = 17;
	cv::erode(bin_img, fg_img, cv::Mat(), cv::Point(-1,-1), erodeit);

	// compress height
	double minVal = 255.0;
	for(int y=0; y<fg_img.rows; y++)
	{
		compRows.push_back(char_img.row(y));
		cv::minMaxLoc(fg_img.row(y), &minVal, NULL, NULL, NULL);
		if(minVal == 255.0)
			compRows.pop_back(1);
	}
	// rotate
	cv::Mat rot_img, rot_fg_img;
	cv::transpose(fg_img, rot_fg_img);
	cv::transpose(compRows, rot_img);
	// compress width
	minVal = 255.0;
	for(int x=0; x<rot_img.rows; x++)
	{
		compCols.push_back(rot_img.row(x));
		cv::minMaxLoc(rot_fg_img.row(x), &minVal, NULL, NULL, NULL);
		if(minVal == 255)
			compCols.pop_back(1);
	}
	cv::transpose(compCols, dst_img);
	// unsharp mask
	// cv::GaussianBlur(dst_img, sharpen, cv::Size(0,0), 3);
	// cv::addWeighted(dst_img, 1.5, sharpen, -0.5, 0, sharpen);
	os << fileName << "_compress.png";
	double mag = std::min<double>(758.0/dst_img.cols, 1024.0/dst_img.rows);
	cv::resize(dst_img, compressed, cv::Size(), mag, mag, cv::INTER_LINEAR);
	cv::imwrite(os.str(), compressed);

	return 0;
}