c++使用std_image.c來載入jpg,png,gif等格式圖片

#include <windows.h>#include <tchar.h>#include <WindowsX.h>HINSTANCE hInst;#pragma comment(lib,"Msimg32.lib")extern "C"{    extern unsigned char *stbi_load_from_memory(unsigned char const *buffer, int len, int *x, int *y,int *comp, int req_comp);    extern void     stbi_image_free(void *retval_from_stbi_load);};LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);LRESULT OnPaint(HWND hWnd, WPARAM wParam, LPARAM lParam);int APIENTRY _tWinMain(HINSTANCE hInstance,HINSTANCE,LPTSTR,int nCmdShow){    hInst = hInstance; // Store instance handle in our global variable    WNDCLASSEX wcex;    wcex.cbSize = sizeof(WNDCLASSEX);    wcex.style            = CS_HREDRAW | CS_VREDRAW;    wcex.lpfnWndProc    = WndProc;    wcex.cbClsExtra        = 0;    wcex.cbWndExtra        = 0;    wcex.hInstance        = hInstance;    wcex.hIcon            = NULL;    wcex.hCursor        = LoadCursor(NULL, IDC_ARROW);    wcex.hbrBackground    = (HBRUSH)(COLOR_BACKGROUND);    wcex.lpszMenuName    = NULL;    wcex.lpszClassName    = _T("std_image.c");    wcex.hIconSm        = NULL;    if(!RegisterClassEx(&wcex)) return FALSE;    HWND hWnd = CreateWindow(_T("std_image.c"), _T("std_image.c"), WS_OVERLAPPEDWINDOW,        CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);    DWORD dw = GetLastError();    if (!hWnd)    {        return FALSE;    }    ShowWindow(hWnd, nCmdShow);    UpdateWindow(hWnd);        MSG msg;    // Main message loop:    while (GetMessage(&msg, NULL, 0, 0))    {        TranslateMessage(&msg);        DispatchMessage(&msg);    }    return (int) msg.wParam;}LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam){    switch (message)    {    case WM_PAINT:        {            OnPaint(hWnd,wParam,lParam);        }break;    case WM_DESTROY:        PostQuitMessage(0);        break;    default:        return DefWindowProc(hWnd, message, wParam, lParam);    }    return 0;}LRESULT OnPaint(HWND hWnd,WPARAM wParam, LPARAM lParam){    PAINTSTRUCT ps;                HDC hdc = BeginPaint(hWnd, &ps);    HANDLE hFile = ::CreateFile(_T("test.png"), GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, \        FILE_ATTRIBUTE_NORMAL, NULL);    if( hFile == INVALID_HANDLE_VALUE ) return NULL;    DWORD dwSize = ::GetFileSize(hFile, NULL);    if( dwSize == 0 ) return NULL;    DWORD dwRead = 0;    LPBYTE pData = new BYTE[ dwSize ];    ::ReadFile( hFile, pData, dwSize, &dwRead, NULL );    ::CloseHandle( hFile );    if( dwRead != dwSize ) {        delete[] pData;        return NULL;    }    LPBYTE pImage = NULL;    int x,y,n;    pImage = stbi_load_from_memory(pData, dwSize, &x, &y, &n, 4);    delete[] pData;    if( !pImage ) return NULL;    BITMAPINFO bmi;    ::ZeroMemory(&bmi, sizeof(BITMAPINFO));    bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);    bmi.bmiHeader.biWidth = x;    bmi.bmiHeader.biHeight = -y;    bmi.bmiHeader.biPlanes = 1;    bmi.bmiHeader.biBitCount = 32;    bmi.bmiHeader.biCompression = BI_RGB;    bmi.bmiHeader.biSizeImage = x * y * 4;    bool bAlphaChannel = false;    LPBYTE pDest = NULL;    HBITMAP hBitmap = ::CreateDIBSection(NULL, &bmi, DIB_RGB_COLORS, (void**)&pDest, NULL, 0);    if( !hBitmap ) return NULL;//     for( int i = 0; i < x * y; i++ ) //     {//         pDest[i*4 + 3] = pImage[i*4 + 3];//         if( pDest[i*4 + 3] < 255 )//RGBA//         {//             pDest[i*4] = (BYTE)(DWORD(pImage[i*4 + 2])*pImage[i*4 + 3]/255);//             pDest[i*4 + 1] = (BYTE)(DWORD(pImage[i*4 + 1])*pImage[i*4 + 3]/255);//             pDest[i*4 + 2] = (BYTE)(DWORD(pImage[i*4])*pImage[i*4 + 3]/255); //             bAlphaChannel = true;//         }//         else // = 255//         {//             pDest[i*4] = pImage[i*4 + 2];//             pDest[i*4 + 1] = pImage[i*4 + 1];//             pDest[i*4 + 2] = pImage[i*4]; //         }// //         if( *(DWORD*)(&pDest[i*4]) == 0 ) {//             pDest[i*4] = (BYTE)0;//             pDest[i*4 + 1] = (BYTE)0;//             pDest[i*4 + 2] = (BYTE)0; //             pDest[i*4 + 3] = (BYTE)0;//             bAlphaChannel = true;//         }//     }    memcpy(pDest,pImage,bmi.bmiHeader.biSizeImage);    stbi_image_free(pImage);    HDC hMemdc = CreateCompatibleDC(hdc);    SelectBitmap(hMemdc,hBitmap);    BLENDFUNCTION ftn = { 0 };    ftn.BlendOp = AC_SRC_OVER;                                                        // 目前只能設定這個值    ftn.AlphaFormat = AC_SRC_ALPHA;                                                      // 也只能設定這個值    ftn.BlendFlags = 0;                                                               // 必須為0    ftn.SourceConstantAlpha = 255;                                                    // 指定源圖片的alpha    AlphaBlend(hdc,0,0,x,y,hMemdc,0,0,x,y,ftn);    EndPaint(hWnd, &ps);    return 0;}

20121030更正: 上面屏蔽代碼不能使用一下代碼替代

memcpy(pDest,pImage,bmi.bmiHeader.biSizeImage);

因為源碼說明 // if you set req_comp to 4, you will always get RGBA output, 所以我應該將其轉換成位元影像的儲存格式BGRA, 上次沒有發現問題, 原因應該是測試的圖片是灰階圖片, RGB值是一樣的