Reputation: 162
I've been trying to convert this JavaScript code that gets the dominant color from an image, so far with no success. I get errors with the colorCount
& color
variables. I don't know the suitable & equivalent data types to use for these variables. Here is my code:
public string dominantColor(Bitmap img)
{
int[] colorCount = new int[0];
int maxCount = 0;
string dominantColor = "";
// data is an array of a series of 4 one-byte values representing the rgba values of each pixel
Bitmap Bmp = new Bitmap(img);
BitmapData BmpData = Bmp.LockBits(new Rectangle(0, 0, Bmp.Width, Bmp.Height), ImageLockMode.ReadOnly, Bmp.PixelFormat);
byte[] data = new byte[BmpData.Stride * Bmp.Height];
for (int i = 0; i < data.Length; i += 4)
{
// ignore transparent pixels
if (data[i+3] == 0)
continue;
string color = data[i] + "." + data[i+1] + "," + data[i+2];
// ignore white
if (color == "255,255,255")
continue;
if (colorCount[color] != 0)
colorCount[color] = colorCount[color] + 1;
else
colorCount[color] = 0;
// keep track of the color that appears the most times
if (colorCount[color] > maxCount)
{
maxCount = colorCount[color];
dominantColor = color.ToString;
}
}
string rgb = dominantColor.Split(",");
return rgb;
}
Upvotes: 4
Views: 179
Reputation: 3189
I'll give you a complete managed version of your code:
static Color dominantColor(Bitmap img)
{
Hashtable colorCount = new Hashtable();
int maxCount = 0;
Color dominantColor = Color.White;
for (int i = 0; i < img.Width; i++)
{
for (int j = 0; j < img.Height; j++)
{
var color = img.GetPixel(i, j);
if (color.A == 0)
continue;
// ignore white
if (color.Equals(Color.White))
continue;
if (colorCount[color] != null)
colorCount[color] = (int)colorCount[color] + 1;
else
colorCount.Add(color, 0);
// keep track of the color that appears the most times
if ((int)colorCount[color] > maxCount)
{
maxCount = (int)colorCount[color];
dominantColor = color;
}
}
}
return dominantColor;
}
So what is the difference here? - I use a Hashtable instead of your array (you never redefine the dimension of it - and the best way to use an extensible object from JavaScript is a Hashtable) - I prefer to use the already included structure Color (which saves 4 bytes for Alpha, Red, Green, Blue) - I also do the comparisons and return this structure (then you are free to do whatever you want to do - in JavaScript using those strings is just a workaround because the browser is just giving you such RGB(a) strings)
What is another problem in your code is the line containing byte[] data = new byte[BmpData.Stride * Bmp.Height]; - Your array is created and initialized but with no data (.NET will erase all previous data resulting in a lot of zeros). Therefore you will not anywhere.
Drawback of my version is that it is indeed very small (this is where your lockbits are coming into play). I can give you a non-managed version (using the lockbits and an unsafe-block) if you want to. Depends if performance matters a lot for you and if you are interested!
Upvotes: 4