c# bitmap filling

Question

I want to create a bitmap of size 160*160 and split it into four squares with each square filled with one color. How can this be done?

Solution 1

Just in case anyone needs a method solving this specific problem in a more general way, I wrote an extension method, taking colors and an integer that states how many tiles it should split off in x and y direction:

public static void FillImage(this Image img, int div, Color[] colors)
{
    if (img == null) throw new ArgumentNullException();
    if (div < 1) throw new ArgumentOutOfRangeException();
    if (colors == null) throw new ArgumentNullException();
    if (colors.Length < 1) throw new ArgumentException();

    int xstep = img.Width / div;
    int ystep = img.Height / div;
    List<SolidBrush> brushes = new List<SolidBrush>();
    foreach (Color color in colors)
        brushes.Add(new SolidBrush(color));

    using (Graphics g = Graphics.FromImage(img))
    {
        for (int x = 0; x < div; x++)
            for (int y = 0; y < div; y++)
                g.FillRectangle(brushes[(y * div + x) % colors.Length], 
                    new Rectangle(x * xstep, y * ystep, xstep, ystep));
    }
}

The four squares, the OP wanted would be produced with:

new Bitmap(160, 160).FillImage(2, new Color[] 
                                  { 
                                      Color.Red, 
                                      Color.Blue, 
                                      Color.Green,
                                      Color.Yellow 
                                  });

Solution 2

You can try something like

using (Bitmap b = new Bitmap(160, 160))
using (Graphics g = Graphics.FromImage(b))
{
    g.FillRectangle(new SolidBrush(Color.Blue), 0, 0, 79, 79);
    g.FillRectangle(new SolidBrush(Color.Red), 79, 0, 159, 79);
    g.FillRectangle(new SolidBrush(Color.Green), 0, 79, 79, 159);
    g.FillRectangle(new SolidBrush(Color.Yellow), 79, 79, 159, 159);
    b.Save(@"c:\test.bmp");
}

Comments

[user1703401]

It is off by one, Right and Bottom are not drawn. Just divide by 2.

[Philip Daubmeier]

The fourth and fifth parameter of FillRectangle are width and height not 'end-x/y-values', so it should be 80 instead of 159. And like Hans Passant said, 80 instead of 79 as x and y parameters.