Cannot save Bitmap in Unity

Unity Engine
1

Hi

I wrote some code to split an image into three files containing either red, green and blue channel.
It’s working properly in a visual studio project but when executing it in unity (Version 5.1.1p2 (82544090e14f) Personal, 64bit) the call of bitmap.save results in the following exception:

InvalidOperationException: The operation is invalid [GDI+ status: Win32Error]
System.Drawing.GDIPlus.CheckStatus (Status status)
System.Drawing.Image.Save (System.String filename, System.Drawing.Imaging.ImageCodecInfo encoder, System.Drawing.Imaging.EncoderParameters encoderParams)
System.Drawing.Image.Save (System.String filename, System.Drawing.Imaging.ImageFormat format)
System.Drawing.Image.Save (System.String filename)
(wrapper remoting-invoke-with-check) System.Drawing.Image:Save (string)
ColorSplitter.splitTextureCopy (System.String imagePath) (at Assets/scripts/Editor/ColorSplitter.cs:171)
ColorSplitter.SplitTexture () (at Assets/scripts/Editor/ColorSplitter.cs:30)

The code triggering the error

    private static Bitmap GetArgbCopy(Image sourceImage)
    {
        Bitmap bmpNew = new Bitmap(sourceImage.Width, sourceImage.Height, PixelFormat.Format32bppArgb);

        using (System.Drawing.Graphics graphics = System.Drawing.Graphics.FromImage(bmpNew))
        {
            graphics.DrawImage(sourceImage, new Rectangle(0, 0, bmpNew.Width, bmpNew.Height), new Rectangle(0, 0, bmpNew.Width, bmpNew.Height), GraphicsUnit.Pixel);
            graphics.Flush();
        }

        return bmpNew;
    }

    public static void splitTextureCopy(string imagePath)
    {
        // the original unconverted image
        Image sourceImage = Image.FromFile(imagePath);

        // copies of original image for red channel
        Bitmap redBmp = GetArgbCopy(sourceImage);
        Bitmap greenBmp = GetArgbCopy(sourceImage);
        Bitmap blueBmp = GetArgbCopy(sourceImage);

        Rectangle rect = new Rectangle(0, 0, sourceImage.Width, sourceImage.Height);

        // safe space for image data in RAM
        BitmapData redBmpData = redBmp.LockBits(rect, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
        BitmapData greenBmpData = greenBmp.LockBits(rect, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
        BitmapData blueBmpData = blueBmp.LockBits(rect, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

        // pointer to first pixel data
        IntPtr redPointer = redBmpData.Scan0;
        IntPtr greenPointer = greenBmpData.Scan0;
        IntPtr bluePointer = blueBmpData.Scan0;

        int bufferSize = redBmpData.Stride * redBmp.Height;
        // byte array containing raw color-data
        byte[] redByteBuffer = new byte[bufferSize];
        byte[] greenByteBuffer = new byte[bufferSize];
        byte[] blueByteBuffer = new byte[bufferSize];

        // copy raw color-data to byte arrays
        Marshal.Copy(redPointer, redByteBuffer, 0, bufferSize);
        Marshal.Copy(greenPointer, greenByteBuffer, 0, bufferSize);
        Marshal.Copy(bluePointer, blueByteBuffer, 0, bufferSize);

        // convert colors in byte array
        // byteBuffer[i] addresses red channel, byteBuffer[i+1] green, byteBuffer[i+2] blue, byteBuffer[i+3] alpha
        for (int i = 3; i < bufferSize; i += 4)
        {
            redByteBuffer[i] = redByteBuffer[i - 1];
            greenByteBuffer[i] = greenByteBuffer[i - 2];
            blueByteBuffer[i] = blueByteBuffer[i - 3];
        }

        // copy color-data back to RAM
        Marshal.Copy(redByteBuffer, 0, redPointer, bufferSize);
        Marshal.Copy(greenByteBuffer, 0, greenPointer, bufferSize);
        Marshal.Copy(blueByteBuffer, 0, bluePointer, bufferSize);

        //free space in RAM
        redBmp.UnlockBits(redBmpData);
        greenBmp.UnlockBits(greenBmpData);
        blueBmp.UnlockBits(blueBmpData);
        redBmpData = null;
        greenBmpData = null;
        blueBmpData = null;
        redByteBuffer = null;
        greenByteBuffer = null;
        blueByteBuffer = null;
        //get name and path of new image
        int index = imagePath.LastIndexOf("/");
        string basePath = imagePath.Substring(0, index);
        string fileName = imagePath.Substring(index + 1);

        //save new image
        redBmp.Save(basePath + "red/" + fileName);
        greenBmp.Save(basePath + "green/" + fileName);
        blueBmp.Save(basePath + "blue/" + fileName);
    }

Could this be due to the NET-Version of Unity?
Thanks

2

System.Drawing doesn’t really work from within unity. In Microsoft .NET world it’s usually mapped to the GDI+ Windows Drawing API, but supporting than in unity or mono across all the different devices it needs to run on? I’d be wary of using that in a pure Mono app, in Unity I’d be shocked if it worked even on Windows.

3

So, the code is correlated with this thread. Is there another way to save the generated bitmap or rather create a light cookie with it in another way?

4

I’d revaluate your problem, creating images/textures on the fly at runtime is not going to get you a good result.

You’d be better of writing your own decal system.

5

As far as I know, the rsult of a decal-system is very similar to a projector’s one. I.e. I only can define a far-clipping-plane which would lead to the problem of missing shadows when not projecting with an angle of 90°.
The result I want to have is the left one but when using projector or decal, I’ll get the right one.

6

I still don’t really know what you’re trying to do here. You seem to be asking for a specific solution to something without really explaining what the problem is that you’re trying to solve.

7

What I’m actually trying to do is to project multiple real-time camera-streams of a surveillance-system back onto a 3D-model of the floor filmed by these cameras.