'System.AccessViolationException' occurred in OpenTK.dll when loading a texture

Question

So I am currently working on a 3D OpenGL game engine in C# using OpenTK, but I ran into a problem when I went to add texture loading

I get this error

An unhandled exception of type 'System.AccessViolationException' occurred in OpenTK.dll Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

I'm not 100% sure why I'm getting a "memory corruption" error, I shouldn't, I've used this code before and I'm just now getting this error.

here is my code:

`

    public static int UploadTexture(string pathname)
    {
        // Create a new OpenGL texture object
        int id = GL.GenTexture(); //THIS IS THE LINE VISUAL STUDIO POINTS OUT WHEN I GET THE ERROR

        // Select the new texture
        GL.BindTexture(TextureTarget.Texture2D, id);

        // Load the image
        Bitmap bmp = new Bitmap(pathname);

        // Lock image data to allow direct access
        BitmapData bmp_data = bmp.LockBits(
                new Rectangle(0, 0, bmp.Width, bmp.Height),
                System.Drawing.Imaging.ImageLockMode.ReadOnly,
                System.Drawing.Imaging.PixelFormat.Format32bppArgb);

        // Import the image data into the OpenGL texture
        GL.TexImage2D(TextureTarget.Texture2D,
                      0,
                      PixelInternalFormat.Rgba,
                      bmp_data.Width,
                      bmp_data.Height,
                      0,
                      OpenTK.Graphics.OpenGL.PixelFormat.Bgra,
                      OpenTK.Graphics.OpenGL.PixelType.UnsignedByte,
                      bmp_data.Scan0);

        // Unlock the image data
        bmp.UnlockBits(bmp_data);

        // Configure minification and magnification filters
        GL.TexParameter(TextureTarget.Texture2D,
                TextureParameterName.TextureMinFilter,
                (int)TextureMinFilter.Linear);
        GL.TexParameter(TextureTarget.Texture2D,
                TextureParameterName.TextureMagFilter,
                (int)TextureMagFilter.Linear);

        // Return the OpenGL object ID for use
        return id;
    }

`

Answer 1

Problems like your's are usually associated with out-of-bounds memory access. While C# and the CLI offer a memory safe execution environment OpenGL itself is an unsafe API and unless you're using a wrapper that performs certain validations before calling OpenGL this can happen.

So what's the most likely cause for your trouble? Why would OpenGL access memory out of bounds? One word: Alignment!

By default OpenGL assumes that image rows are aligned to 4 byte boundaries. Say that your actual image data rows are aligned to 1 byte boundaries, your image width is a multiple of 3 but neither 2 nor 4 then OpenGL will read image height times 3 bytes beyond the memory region actually occupied by your image.

The solution is simple: Tell OpenGL the alignment of your image data. For BMP sections it happens to be 1 byte alignments. Add this before your glTexImage2D call:

GL.PixelStore(PixelStoreParameter.UnpackAlignment, 1);