代码写了两个小时，速度太慢（包括学习文档的时间）

#include <stdio.h>
#include <Windows.h>
#include <gdiplus.h>
#include <string.h>
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;
}