使用GDI+、文件和目录和打印API，批量将图片按文件名分组打包成PDF

代码写了两个小时，速度太慢（包括学习文档的时间）

#include 
#include 
#include 
#include 
using namespace Gdiplus;
#pragma comment(lib, "Gdiplus.lib")
enum {
	IDLEN=30,
	FNAME=IDLEN+5,//.pdf
};

int main(void) {
	GdiplusStartupInput gsi;
	ULONG_PTR tok;
	GdiplusStartup(&tok,&gsi,nullptr);
	HDC print=CreateDCA("WINSPOOL","Microsoft Print to PDF",nullptr,nullptr);

	SetCurrentDirectoryA("D:\\pic2pdf");
	WIN32_FIND_DATAW fd;
	HANDLE hf=FindFirstFileW(L"*.jpg",&fd);
	if (hf) {
		puts("找到了jpg文件");

		wchar_t f[FNAME];
		wchar_t* p=wcschr(fd.cFileName,L'_');
		wcsncpy(f,fd.cFileName,p-fd.cFileName);
		wcscpy(p-fd.cFileName+f,L".pdf");

		DOCINFOW doc{};
		doc.cbSize=sizeof doc;
		doc.lpszDocName=doc.lpszOutput=f;
		StartDocW(print,&doc);
		StartPage(print);
		Graphics g(print);

		while (true) {
			Image img(fd.cFileName);
			g.DrawImage(&img,0,0);
			EndPage(print);

			if (FindNextFileW(hf,&fd)) {
				wchar_t f1[FNAME];
				p=wcschr(fd.cFileName,L'_');
				wcsncpy(f1,fd.cFileName,p-fd.cFileName);
				wcscpy(p-fd.cFileName+f1,L".pdf");
				if (wcscmp(f,f1)) {
					EndDoc(print);
					wprintf(L"%s\n",f);
					wcscpy(f,f1);
					StartDocW(print,&doc);
				}
			} else {
				EndDoc(print);
				wprintf(L"%s\n",f);
				break;
			}
		};
	}
	return 0;
}