You have a few problems that I can see. The biggest issue is that your image has a width of 200, but in memory, its stride is 600 (for me - probably similar for you). This means you are writing out a lot more data, because you don't ignore the 400 padding pixels per row.
Other issues:
- You're timing string concatenation only. By the time you start your timer, the lockbits stuff has finished.
- Your string concatenation would be faster using StringBuilder.
- You are locking the bitmap for read/write access, when you only need read. No discernible effect on performance for me, with this image, but still might as well change it to ReadOnly.
- Most of your comments are unnecessary at best (
// creates array
)- some are misleading (//Scans the first line of data
- no, it returns a pointer to the data which has already been loaded).
The following code completes in only a few milliseconds on my machine.
Bitmap bmp = new Bitmap(@"d:\stripe.jpg");
//pictureBox1.Image = bmp;
Stopwatch Timer = new Stopwatch();
Rectangle bmpRec = new Rectangle(0, 0, bmp.Width, bmp.Height);
BitmapData bmpData = bmp.LockBits(
bmpRec, ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
IntPtr Pointer = bmpData.Scan0;
int DataBytes = Math.Abs(bmpData.Stride) * bmp.Height;
byte[] rgbValues = new byte[DataBytes];
Marshal.Copy(Pointer, rgbValues, 0, DataBytes);
bmp.UnlockBits(bmpData);
StringBuilder pix = new StringBuilder(" ");
Timer.Start();
for (int i = 0; i < bmpData.Width; i++)
{
for (int j = 0; j < bmpData.Height; j++)
{
// compute the proper offset into the array for these co-ords
var pixel = rgbValues[i + j*Math.Abs(bmpData.Stride)];
pix.Append(" ");
pix.Append(pixel);
}
}
Timer.Stop();
Console.WriteLine(Timer.Elapsed);