Many a times we come across to situations where we need to find out whether a given pixel in an image is a solid pixel or a Transparent Pixel.

We have an image property called alpha value which tells us about the transparency of image. A pixel can be of three types depending upon its alpha value:

1. Opaque = 255(if Alpha value is 255)
2. Translucent = 1-254(if Alpha value between 0-254)
3.Transparent = 0(if Alpha value is 0)

Here is the short C# program which identifies the transparency of image on above mentioned alpha values:

        int xPixel = 50;//Xpixel of point for which we want to check transparency
        int yPixel = 50;//Ypixel of point for which we want to check transparency

        int transparent = 0;//Alpha code of translucent is 0
        int translucent = 254;//Alpha code of translucent is 1-254

        Bitmap bitmapInstance = (Bitmap)Image.FromFile("C:/Users/User/Desktop/Test.png");//Get Image Instance
        byte alphaValue = bitmapInstance.GetPixel(xPixel, yPixel).A;//Get alpha value of Point

        if (alphaValue == transparent)
            MessageBox.Show("Pixel is Transparent");
        else if (alphaValue <= translucent)
            MessageBox.Show("Pixel is Translucent");
        else
            MessageBox.Show("Pixel is Opaque");//>254 is Opaque

Using the above code we can identify the alpha value and transparency of pixel