Question

I want to develop a basic tool like the one featured here. I will be taking screenshots of a number of web pages and from there I wish to take the top five most popular colours and from there somehow decide whether the colours are a good match.

I want to write this tool in C# and after a bit of research I discovered lockbits. My first idea was to take an image and then get the colour of each pixel, but I am unsure as to whether this will give me the results I desire and how to make six lists of the most popular colours.

Can anyone here provide advice as to how I would create a program to do something similar to the program above, that will take in an image and will select the top five colours used in the image?

Answer 1

Well.. Use a thumbnail image (16×16, 32×32 etc) and select from it the colors like

updated code:

    private void button1_Click(object sender, EventArgs e)
    {
        int thumbSize = 32;
        Dictionary<Color, int> colors = new Dictionary<Color, int>();

        Bitmap thumbBmp = 
            new Bitmap(pictureBox1.BackgroundImage.GetThumbnailImage(
                thumbSize, thumbSize, ThumbnailCallback, IntPtr.Zero));

        //just for test
        pictureBox2.Image = thumbBmp;            

        for (int i = 0; i < thumbSize; i++)
        {
            for (int j = 0; j < thumbSize; j++)
            {
                Color col = thumbBmp.GetPixel(i, j);
                if (colors.ContainsKey(col))
                    colors[col]++;
                else
                    colors.Add(col, 1);
            }                
        }

        List<KeyValuePair<Color, int>> keyValueList = 
            new List<KeyValuePair<Color, int>>(colors);

        keyValueList.Sort(
            delegate(KeyValuePair<Color, int> firstPair,
            KeyValuePair<Color, int> nextPair)
            {
                return nextPair.Value.CompareTo(firstPair.Value);
            });

        string top10Colors = "";
        for (int i = 0; i < 10; i++)
        {
            top10Colors += string.Format("\n {0}. {1} > {2}",
                i, keyValueList[i].Key.ToString(), keyValueList[i].Value);
            flowLayoutPanel1.Controls[i].BackColor = keyValueList[i].Key;
        }
        MessageBox.Show("Top 10 Colors: " + top10Colors);
    }

    public bool ThumbnailCallback() { return false; }

alt text http://lh3.ggpht.com/_1TPOP7DzY1E/S0uZ6GGD4oI/AAAAAAAAC5k/3Psp1cOCELY/s800/colors.png