在《批量下载网络图片到本地》里写到了批量下载图片，其实那些图片是电子地图的散片，我想把这些图片合成一张大图，以便做成可以直接打开查看的地图甚至把印成纸质地图。当然这一切可以用图片处理软件一张一张地拼接，但地图散片动不动就是成百上千片，手动处理会很累，于是我选择了C++，代码很简单，同时这也得益于lodepng库的引入:

#include <vector>

#include <urlmon.h>

#include <string>

#include <iostream>

#include "loadpng.h"

using namespace std;

#pragma comment(lib, "urlmon.lib")



#define ROW	10

#define COL	9

#define PIC_WIDTH	256

#define PIC_HEIGHT	256



void decodeOneStep()

{

	std::vector<unsigned char> image_ret(ROW*COL*PIC_WIDTH*PIC_HEIGHT*4);

	std::vector<unsigned char> image[ROW][COL];

	unsigned width = 0; 

	unsigned height = 0;

	unsigned error = 0;

	unsigned int idx_row;

	unsigned int idx_col;

	char filename[100];

	unsigned int idx_row_tmp;

	unsigned int idx_col_tmp;

	unsigned int x;

	unsigned int y;

	unsigned int pos;

	const char *out = "out.png";



	for (idx_row = 0; idx_row < ROW; idx_row++) {

		for (idx_col = 0; idx_col < COL; idx_col++) {

			sprintf(filename, "map/%d_%d.png", idx_col, (ROW-idx_row-1));

			error = lodepng::decode(image[idx_row][idx_col], width, height, filename);

			printf("file:%s  w:%d h:%d\n", filename, width, height);

			if (error) {

				printf("decoder error:%d  %s\n", error, lodepng_error_text(error));

			}

			if (width != PIC_WIDTH || height != PIC_HEIGHT) {

				printf(" error size of pic \n");

			}



			pos = 0;

			for (idx_row_tmp = 0; idx_row_tmp < height; idx_row_tmp++) {

				for (idx_col_tmp = 0; idx_col_tmp < width; idx_col_tmp++) {

					x = idx_col * PIC_WIDTH + idx_col_tmp;

					y = idx_row * PIC_HEIGHT + idx_row_tmp;

					image_ret[(y * PIC_WIDTH * COL + x) * 4] = image[idx_row][idx_col][(pos*4)];

					image_ret[(y * PIC_WIDTH * COL + x) * 4 + 1] = image[idx_row][idx_col][(pos * 4 + 1)];

					image_ret[(y * PIC_WIDTH * COL + x) * 4 + 2] = image[idx_row][idx_col][(pos * 4 + 2)];

					image_ret[(y * PIC_WIDTH * COL + x) * 4 + 3] = image[idx_row][idx_col][(pos * 4 + 3)];

					pos++;

				}

			}





		}

	}

	printf("image ******* len:%u\n", image_ret.size());

	lodepng::encode(out, image_ret, PIC_WIDTH * COL, PIC_HEIGHT * ROW);



}



int main(int argc, char *argv[])

{

	decodeOneStep();

	system("pause");

}