Convert 8bpp Image to Qimage

[pyromanci]

I had a program i originally wrote in C#, but I need it to run on linux now. So I've been porting it to c++ to use the QT GUI. It's almost done say for 1 thing. I have a few biometeric libraries (fingerprint, palm, and facial) that are used for authentication.

I have those 3 working for the most part. One thing I do in the c# version is show the captured image from the biometeric readers. Problem is I really suck and Image processing and converting formats. Both the Palm and Fingerprint scanners return a raw 8bpp image (no headers). Where as the Facial recognition library is a Jpeg format.

In my c# version I convert the 8bpp images to jpegs using this function:

public byte[] CreateRawJpegFrom8BPP(byte[] bytes, int width, int height)
        {
            byte[] rgbBytes = new byte[bytes.Length * 3];
 
            for (int i = 0; i <= bytes.Length - 1; i++)
            {
                rgbBytes[(i * 3)] = bytes[i];
                rgbBytes[(i * 3) + 1] = bytes[i];
                rgbBytes[(i * 3) + 2] = bytes[i];
            }
            Bitmap bmp = new Bitmap(width, height, PixelFormat.Format24bppRgb);
 
            BitmapData data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb);
 
            for (int i = 0; i <= bmp.Height - 1; i++)
            {
                long s = data.Scan0.ToInt64();
                int l = data.Stride;
 
                IntPtr p = new IntPtr(data.Scan0.ToInt64() + data.Stride * i);
                System.Runtime.InteropServices.Marshal.Copy(rgbBytes, i * bmp.Width * 3, p, bmp.Width * 3);
            }
 
            bmp.UnlockBits(data);
 
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
            byte[] byteImage = ms.ToArray();
            ms.Close();
            ms.Dispose();
 
            return byteImage ;
        }

public byte[] CreateRawJpegFrom8BPP(byte[] bytes, int width, int height)
        {
            byte[] rgbBytes = new byte[bytes.Length * 3];

            for (int i = 0; i <= bytes.Length - 1; i++)
            {
                rgbBytes[(i * 3)] = bytes[i];
                rgbBytes[(i * 3) + 1] = bytes[i];
                rgbBytes[(i * 3) + 2] = bytes[i];
            }
            Bitmap bmp = new Bitmap(width, height, PixelFormat.Format24bppRgb);

            BitmapData data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb);

            for (int i = 0; i <= bmp.Height - 1; i++)
            {
                long s = data.Scan0.ToInt64();
                int l = data.Stride;

                IntPtr p = new IntPtr(data.Scan0.ToInt64() + data.Stride * i);
                System.Runtime.InteropServices.Marshal.Copy(rgbBytes, i * bmp.Width * 3, p, bmp.Width * 3);
            }

            bmp.UnlockBits(data);

            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
            byte[] byteImage = ms.ToArray();
            ms.Close();
            ms.Dispose();

            return byteImage ;
        }

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Now I sure if I could get the Image data into a QImage I could figure out the rest.
I've tired:

/* For refences this is teh structure format.
typedef struct dpfpdd_image_info {
	unsigned int size;    /**< size of the structure */
	unsigned char*        image_data;      /**< image data */
	unsigned int          image_size;      /**< size of the image data */
	unsigned int width;   /**< width of the captured image */
	unsigned int height;  /**< height of the captured image */
	unsigned int res;     /**< resolution of the captured image */
	unsigned int bpp;     /**< pixel depth of the captured image */
 
} DPFPDD_IMAGE_INFO;
*/
 
QImage* img = new QImage(pImageInfo.width, pImageInfo.height, QImage::Format_Indexed8);
img->fromData(pImageInfo.image_data, pImageInfo.image_size);

/* For refences this is teh structure format.
typedef struct dpfpdd_image_info {
	unsigned int size;    /**< size of the structure */
	unsigned char*        image_data;      /**< image data */
	unsigned int          image_size;      /**< size of the image data */
	unsigned int width;   /**< width of the captured image */
	unsigned int height;  /**< height of the captured image */
	unsigned int res;     /**< resolution of the captured image */
	unsigned int bpp;     /**< pixel depth of the captured image */

} DPFPDD_IMAGE_INFO;
*/

QImage* img = new QImage(pImageInfo.width, pImageInfo.height, QImage::Format_Indexed8);
img->fromData(pImageInfo.image_data, pImageInfo.image_size);

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I then try to save it off as a Bitmap to look at it, but i'm told it's not a proper bitmap file.

So i'm not sure if i am even close to the direction on loading this image data into a Qimage.

Any direction would be great. I've been searching around all day, but just have not had much of any luck.

[high_flyer]

I had a program i originally wrote in C#, but I need it to run on linux now. So I've been porting it to c++ to use the QT GUI.

You do know that you can simply use Mono with your C# code on linux don't you?

Is the image data you are loading on to the QImage already converted to jpeg?
The docs say:

If format is not specified (which is the default), the loader probes the file for a header to determine the file format. If format is specified, it must be one of the values returned by QImageReader::supportedImageFormats().

So you might want to specify jpg and see if it helps, since your image data does not have a header.

Did you have a look at how QImage is using indexed8 format and does your code prepares the data accordingly?
http://doc.qt.io/qt-5/qimage.html#image-formats