如何将位图传递给C ++ dll？

Question

The program has no tip errors ,But there is no any picture display in c++ form,Tested the simple data types, such as int, can be normal delivery,please give me a simple example ,tell me what to do

C# Code

[DllImport("dllTestForm.dll", EntryPoint = "showFormC")]
static extern void testShowFormC(byte[] photo,int len);

private void button6_Click(object sender, EventArgs e)
{
        Bitmap bmp = (Bitmap)Image.FromFile(@"d:\1\1.jpg");

        Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
        System.Drawing.Imaging.BitmapData bmpData =
        bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite,bmp.PixelFormat);

        // Get the address of the first line.
        IntPtr ptr = bmpData.Scan0;

        // Declare an array to hold the bytes of the bitmap. 
        int bytes  = Math.Abs(bmpData.Stride) * bmp.Height;
        byte[] rgbValues = new byte[bytes];

         // Copy the RGB values into the array.
         System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes);

         // Unlock the bits.
         bmp.UnlockBits(bmpData);

         testShowFormC(rgbValues, bytes);
}

C++ Code

void __stdcall showFormC(byte *photo,int len)
{
    ThelloWorld *a=new ThelloWorld(Application); //winForm,display photo
    a->ImageEnView2->IO->LoadFromBuffer(photo,0,len);  
    a->Show();
}

Answer 1

Buffer got from C# code is not completed.

You only get bitmap pixel data but not header. Header contains info to describe pixel data (8 bit, 16 bit, 24 bit, color palette and so on).

For a->ImageEnView2->IO->LoadFromBuffer(photo,0,len); , I guess you are using TImageEnIO component. From help http://www.imageen.com/help/ImageEn/TImageEnIO.LoadFromBuffer.html , why not pass whole jpeg file data to LoadFromBuffer ?

Answer 2

You can use Bitmap.Save() method to convert it to a memory stream and then send it to C++ dll .

image.Save(imageMemoryStream, System.Drawing.Imaging.ImageFormat.Png);

Then, in C++ dll use decoding such as cv::imdecode() method to get the image.

Details are here .