JPG图片缩略图与原图不一致(VC6源码)

#include <windows.h> #include <gdiplus.h> #include <commctrl.h> #include "resource.h" using namespace Gdiplus; #pragma comment(lib, "gdiplus.lib") #pragma comment(lib, "comctl32.lib") int GetEncoderClsid(const WCHAR* format, CLSID* pClsid) { UINT num = 0; // number of image encoders UINT size = 0; // size of the image encoder array in bytes ImageCodecInfo* pImageCodecInfo = NULL; GetImageEncodersSize(&num, &size); if(size == 0) return -1; // ailure pImageCodecInfo = (ImageCodecInfo*)(malloc(size)); if (pImageCodecInfo == NULL) return -1; // Failure GetImageEncoders(num, size, pImageCodecInfo); for(UINT j=0; j<num; ++j) { if(wcscmp(pImageCodecInfo[j].MimeType, format) == 0) { *pClsid = pImageCodecInfo[j].Clsid; free(pImageCodecInfo); return j; // Success } } free(pImageCodecInfo); return -1; // Failure } //初始化“打开”/“另存为”文件对话框窗口 void PopFileInitialize(HWND hwnd, OPENFILENAME *pOfn) { static TCHAR szFilter[] = TEXT ("JPG File (*.jpg)\0*.jpg\0") ; pOfn->lStructSize = sizeof (OPENFILENAME) ; pOfn->hwndOwner = hwnd ; pOfn->hInstance = NULL ; pOfn->lpstrFilter = szFilter ; pOfn->lpstrCustomFilter = NULL ; pOfn->nMaxCustFilter = 0 ; pOfn->nFilterIndex = 0 ; pOfn->lpstrFile = NULL ; // Set in Open and Close functions pOfn->nMaxFile = MAX_PATH ; pOfn->lpstrFileTitle = NULL ; // Set in Open and Close functions pOfn->nMaxFileTitle = MAX_PATH ; pOfn->lpstrInitialDir = NULL ; pOfn->lpstrTitle = NULL ; pOfn->Flags = 0 ; // Set in Open and Close functions pOfn->nFileOffset = 0 ; pOfn->nFileExtension = 0 ; pOfn->lpstrDefExt = TEXT ("jpg") ; pOfn->lCustData = 0L ; pOfn->lpfnHook = NULL ; pOfn->lpTemplateName = NULL ; } //弹出“打开”文件对话框窗口 BOOL PopFileOpenDlg(HWND hwnd, PTSTR pstrFileName, PTSTR pstrTitleName) { OPENFILENAME ofn ; PopFileInitialize(hwnd, &ofn) ; ofn.lpstrFile = pstrFileName ; ofn.lpstrFileTitle = pstrTitleName ; ofn.Flags = OFN_FILEMUSTEXIST | OFN_EXPLORER ; return GetOpenFileName(&ofn) ; } //弹出“另存为”对话框窗口 BOOL PopFileSaveDlg(HWND hwnd, PTSTR pstrFileName, PTSTR pstrTitleName) { OPENFILENAME ofn ; PopFileInitialize(hwnd, &ofn) ; ofn.lpstrFile = pstrFileName ; ofn.lpstrFileTitle = pstrTitleName ; ofn.Flags = OFN_FILEMUSTEXIST | OFN_OVERWRITEPROMPT | OFN_PATHMUSTEXIST ; return GetSaveFileName(&ofn) ; } //根据Image对象保存为jpg文件 BOOL SaveJpg(Image *pImg, const WCHAR *lpwszPath) { CLSID jpgClsid; if(!pImg || !lpwszPath) return FALSE ; GetEncoderClsid(L"image/jpeg", &jpgClsid); if(Ok == pImg->Save(lpwszPath, &jpgClsid, NULL)) return TRUE ; return FALSE ; } //核心函数 lpszDestImg是最终图片保存的路径 BOOL SetJpgThumb(HWND hEditImgSrc, HWND hEditImgThumb, LPCTSTR lpszDestImg) { int iSrcWidth, iSrcHeight, i, iThumbWidth, iThumbHeight ; //iThumbWidth是要生成的临时图片的宽度 WCHAR wszPath[MAX_PATH] ; if(GetWindowTextLength(hEditImgSrc)<=0 || GetWindowTextLength(hEditImgThumb)<=0 || lpszDestImg==NULL) return FALSE ; GetWindowTextW(hEditImgSrc, wszPath, MAX_PATH) ; Image imgSrc(wszPath) ; iSrcWidth = imgSrc.GetWidth() ; //原图宽度 iSrcHeight = imgSrc.GetHeight() ; GetWindowTextW(hEditImgThumb, wszPath, MAX_PATH) ; Image imgThumbSrc(wszPath) ; //计算要生成的缩略图尺寸 if(iSrcWidth>=200 || iSrcHeight>=200) { i = max(iSrcWidth, iSrcHeight) ; i /= 100 ; iThumbWidth = iSrcWidth / i ; iThumbHeight = iSrcHeight / i ; } else { iThumbWidth = iSrcWidth ; iThumbHeight = iSrcHeight ; } Image *pImgThumb = imgThumbSrc.GetThumbnailImage(iThumbWidth, iThumbHeight) ; SaveJpg(pImgThumb, L"$tempjpg$") ; //保存临时图片文件 delete pImgThumb ; //读取临时图片文件的数据 HANDLE hFile = CreateFile(TEXT("$tempjpg$"), GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL) ; if (hFile == INVALID_HANDLE_VALUE) return FALSE ; DWORD dwSize = GetFileSize(hFile, NULL) ; LPVOID data = new BYTE[dwSize] ; ReadFile(hFile, data, dwSize, &dwSize, NULL) ; CloseHandle(hFile) ; DeleteFile(TEXT("$tempjpg$")) ; //删除临时图片文件 //设置图片属性项 PropertyItem propItem ; USHORT us = 0x0002 ; propItem.id = PropertyTagResolutionUnit; //Unit of measure for the horizontal resolution and the vertical resolution. propItem.length = sizeof(us) ; propItem.type = PropertyTagTypeShort; propItem.value = &us ; imgSrc.SetPropertyItem(&propItem); us = 0x0006 ; propItem.id = PropertyTagThumbnailCompression; //Compression scheme used for thumbnail image data. propItem.length = sizeof(us) ; propItem.type = PropertyTagTypeShort; propItem.value = &us ; imgSrc.SetPropertyItem(&propItem); propItem.id = PropertyTagThumbnailData; propItem.length = dwSize ; propItem.type = PropertyTagTypeByte; propItem.value = data ; imgSrc.SetPropertyItem(&propItem); delete data ; #ifdef _UNICODE return SaveJpg(&imgSrc, lpszDestImg) ; #else MultiByteToWideChar(CP_ACP, 0, lpszDestImg, lstrlen(lpszDestImg)+1, wszPath, MAX_PATH); return SaveJpg(&imgSrc, wszPath) ; #endif } //获取图片的矩形区域，根据两个picture控件获取 BOOL GetCtrlRect(HWND hwndMain, int iCtrlId, LPRECT lprc) { POINT pt ; if(!hwndMain || !lprc) return FALSE ; GetWindowRect(GetDlgItem(hwndMain, iCtrlId), lprc) ; pt.x = lprc->left ; pt.y = lprc->top ; ScreenToClient(hwndMain, &pt) ; lprc->right = pt.x + (lprc->right-lprc->left) ; lprc->bottom = pt.y + (lprc->bottom-lprc->top) ; lprc->left = pt.x ; lprc->top = pt.y ; return TRUE ; } //根据Edit控件显示的图片路径，画图 void DrawImage(HWND hwndMain, HWND hEdit, LPRECT lprc) { WCHAR wszPath[MAX_PATH] ; if(!lprc) return ; GetWindowTextW(hEdit, wszPath, MAX_PATH) ; Image img(wszPath) ; Graphics g(hwndMain) ; g.DrawImage(&img, lprc->left, lprc->top, lprc->right-lprc->left, lprc->bottom-lprc->top) ; } BOOL CALLBACK MainDlg(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { static HINSTANCE hInstance ; static HWND hEditImgSrc, hEditImgThumb ; static RECT rcSrc, rcThumbSrc ; //显示区域 HDROP hDrop = NULL ; TCHAR szPath[MAX_PATH]={0} ; //路径 POINT pt ; //拖拽文件到窗口时，当前的鼠标坐标 HDC hdc ; HWND hEdit ; //拖拽文件到窗口时，当前鼠标坐标下的窗口句柄 PAINTSTRUCT ps ; switch(message) { case WM_INITDIALOG: hInstance = (HINSTANCE)lParam ; DragAcceptFiles(hwnd, TRUE) ; //使窗口支持文件拖拽功能 SetClassLong(hwnd, GCL_HICON, (long)LoadIcon(hInstance, MAKEINTRESOURCE(IDI_ICON_MAIN))) ; //设置图标 hEditImgSrc = GetDlgItem(hwnd, IDC_EDIT_IMGSRC) ; hEditImgThumb = GetDlgItem(hwnd, IDC_EDIT_IMGTHUMB) ; GetCtrlRect(hwnd, IDC_IMG_SRC, &rcSrc) ; //获取显示区域 GetCtrlRect(hwnd, IDC_IMG_THUMBSRC, &rcThumbSrc) ; return TRUE ; case WM_DROPFILES: //当文件拖放到窗口时 hDrop = (HDROP)wParam ; DragQueryFile(hDrop, 0, szPath, MAX_PATH) ; //这里我们只支持一个文件 GetCursorPos(&pt) ; //获取当前鼠标坐标 hEdit = WindowFromPoint(pt) ; //根据坐标值取得当前坐标点下的窗口句柄 // 根据句柄比较，看在哪个编辑控件下 if(hEdit == hEditImgSrc) { SetWindowText(hEditImgSrc, szPath) ; InvalidateRect(hwnd, &rcSrc, TRUE) ; } else if(hEdit == hEditImgThumb) { SetWindowText(hEditImgThumb, szPath) ; InvalidateRect(hwnd, &rcThumbSrc, TRUE) ; } return TRUE ; case WM_PAINT: hdc = BeginPaint (hwnd, &ps) ; if(GetWindowTextLength(hEditImgSrc) > 0) DrawImage(hwnd, hEditImgSrc, &rcSrc) ; if(GetWindowTextLength(hEditImgThumb) > 0) DrawImage(hwnd, hEditImgThumb, &rcThumbSrc) ; EndPaint (hwnd, &ps) ; return TRUE ; case WM_CLOSE: EndDialog(hwnd, 0) ; return TRUE ; case WM_COMMAND: switch(LOWORD(wParam