用此法得到了解決。

3. 另一個執行時異常, Debug時出現:
“Unhandled exception at 0×6c1f4774 (msvcr90.dll) in TestMagick.exe: 0xC0000005: Access violation reading location 0xcccccccc.”

同樣在官方論壇上找到答案:是Project屬性配置引起的, Project Properties->Configuration Properties->C/C++->Code Generation->Runtime Library, 把Multi-threaded Debug DLL (/MDd)改為Multi-threaded DLL (/MD)

五月 21st, 2009

在C++中使用ImageMagick(簡稱Magick)處理一些圖片, 碰到幾個問題並嘗試找到了解決方案.

從Magick官方網站下載的ImageMagick-6.5.2-4-Q16-windows-dll.exe, 安裝時選上C++開發包. 開發用的IDE是Visual Studio 2008.

1. Magick對中文的路徑名支援不是很好, 比如

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Image img;
img.read("e://頭像 小頭//小王.jpg");  // 讀取失敗

這種中文路徑在OpenCV中是沒問題的. 不過Magick並非不支援中文路徑名, 只是需要先對中文路徑進行utf-8編碼

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// use utf8 to encode the string and store as char*. Need #include <wtypes.h>.
// Not support linux, ps. iconv can do the same thing in linux.
 

// src -- a string to be converted, may contains characters like Chinese.
// return -- a point to a string which allocated in heap, it should be delete[].
char* acp2utf8(const char* src)
{
    int len = strlen(src);
    int n = MultiByteToWideChar(CP_ACP, 0, src, -1, NULL, 0);
    char* res;
    if (len + 1 == n)
    {
        // all ascii characters, which the same as utf8 encoding string.
        res = new char[n];
        strncpy(res, src, n);
    }
    else
    {
        WCHAR* ws = new WCHAR[n];
        MultiByteToWideChar(CP_ACP, 0, src, -1, ws, n-1);
        ws[n-1] = 0;
 
        n = WideCharToMultiByte(CP_UTF8, 0, ws, -1, NULL, 0, NULL, NULL);
        res = new char[n];
        WideCharToMultiByte(CP_UTF8, 0, ws, -1, res, n-1, NULL, NULL);
        res[n-1] = 0;
 
        delete[] ws;
    }
 
    return res;
}

這樣進行呼叫時, 只要:

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char* fn = acp2utf8("e://頭像 小頭//小王.jpg");
Image img;
img.read(fn);
delete[] fn; // 別忘釋放記憶體

2. 編譯通過, 執行時碰到error(可在Debug模式下看到, Release下可能就直接退出了):
“Application Error
The application failed to initialize properly (0xc00000fd). Click on OK to terminate the application.”

很莫名其妙, 正常安裝應該不會碰到. 重灌系統後, 直接拿上次安裝的dll來用就會出錯這個錯誤. Google到答案: 因為它依賴登錄檔!! 重新安裝一下就好了.
“The binary distribution of ImageMagick for Windows requires an installer to properly set entries in the Windows registry. What you want is an “uninstalled” version of ImageMagick. You will need to build ImageMagick from source which by default permits you to gather the binaries and configuration files into one folder and redistribute them free of dependencies on the Windows registry.”

3. 另一個執行時異常, Debug時出現:
“Unhandled exception at 0×6c1f4774 (msvcr90.dll) in TestMagick.exe: 0xC0000005: Access violation reading location 0xcccccccc.”

同樣在官方論壇上找到答案:是Project屬性配置引起的, Project Properties->Configuration Properties->C/C++->Code Generation->Runtime Library, 把Multi-threaded Debug DLL (/MDd)改為Multi-threaded DLL (/MD), 而/MDd是Debug的預設選項. 不過文中提到的有關”_DEBUG”改為”NDEBUG”倒不必.

“Well, I think I have it…… Turns out I didn’t quite have all the settings the same. But after a series of experiments and keeping track of all changes/differences between Debug and Release I think I’ve got it nailed down. In the “Project Properties” page, under “Configuration Properties/C++/Code Generation” make sure the “Runtime Library” is set to “Multi-Threaded DLL (/MD)” and not to “Multi-Threaded Debug DLL (/MDd)” which is the default for the Debug setup. Then under “Configuration Properties/C++/Preprocessor” you have to change the “Preprocessor Definition” that is set to “_DEBUG” to “NDEBUG”. I assume that this flag is used in the header files for the Magick++.h files somewhere. When I change these two parameters then everything works in the debug build environment.”

至於原因, 查了下MSDN, 找到這麼一句話, “All modules passed to a given invocation of the linker must have been compiled with the same run-time library compiler option (/MD, /MT, /LD). “, 可能可以解釋.