C#Com从设备检索二进制图像（Tiff）数据

我试图使用StringBuilder通过COM检索Tiff图像数据，但COM调用后缓冲区的长度仅为3。我正在将一个VB.NET版本转换为C#，它使用字符串而不是StringBuilder，工作正常。如果有人有任何建议或能给我指一些好的阅读材料，我将不胜感激

COM函数签名：

ULONG MTMICRGetImage (char *pcDevName, char *pcImageID, char *pcBuffer, DWORD *pdwLength

))

COM调用代码：

    ImageSize = Convert.ToInt32(mtValue.ToString());
    TempImage = new StringBuilder(ImageSize);
    mtValueSize = 9216;

    RC = MTMICRGetIndexValue(mtDocInfo, "ImageInfo", "ImageURL", 2, mtValue, ref mtValueSize);

    // Allocate memory for image with size of ImageSize
    RC = MTMICRGetImage(ExcellaDeviceName, mtValue.ToString(), TempImage, ref ImageSize);

---

编辑：我相信这是由于二进制数据及其封送方式造成的，字符串中的字符4是空字符。根据Marshal.PtrToStringAuto（）/Marshal.PtrToStringUni（），复制到第一个空字符之前的所有字符。

我找到了答案。该问题是由于编组时终止StringBuilder的空字符造成的。相反，我必须使用IntPtr并将字节直接从内存中读取到字节数组中。请参阅下面的解决方案

[DllImport("mtxmlmcr", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
static extern Int32 MTMICRGetImages(string DeviceName, ref MagTekImage MagTekGImages, ref Int32 TotalImages);


// 
// Allocate memory for image with size of imageSize, because the image
// data has null characters (which marshalling doesn't like), we must
// get the memory location of the char* and read bytes directly from memory
//
IntPtr ptr = Marshal.AllocHGlobal(imageSize + 1);
RC = MTMICRGetImage(ExcellaDeviceName, mtValue.ToString(), ptr, ref imageSize);

// Copy the Image bytes from memory into a byte array for storing
byte[] imageBytes = new byte[imageSize];
Marshal.Copy(ptr, imageBytes, 0, imageSize);
Marshal.FreeHGlobal(ptr);

---

您确定ImageSize大于3吗？与中一样，ImageSize的值作为最后一个参数传递到MTMIRGETIMAGE。是的，图像大小可以。我将vb.net版本更改为使用StringBuilder，并且遇到了与C代码相同的问题。这3个字符是tiff文件头“ll*”的开头（在Ascii中，*=十进制表示42）。我会仔细检查大小以确保。图像大小很好，StringBuilder根据图像大小提供了最大容量，例如10754，但在COM调用之后，它的长度仅为3。灵感来自

[DllImport("mtxmlmcr", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
static extern Int32 MTMICRGetImages(string DeviceName, ref MagTekImage MagTekGImages, ref Int32 TotalImages);


// 
// Allocate memory for image with size of imageSize, because the image
// data has null characters (which marshalling doesn't like), we must
// get the memory location of the char* and read bytes directly from memory
//
IntPtr ptr = Marshal.AllocHGlobal(imageSize + 1);
RC = MTMICRGetImage(ExcellaDeviceName, mtValue.ToString(), ptr, ref imageSize);

// Copy the Image bytes from memory into a byte array for storing
byte[] imageBytes = new byte[imageSize];
Marshal.Copy(ptr, imageBytes, 0, imageSize);
Marshal.FreeHGlobal(ptr);