[Selective Transparency]

This plugin will take the brightness of the pixels in an image, and make them transparent based on the values from the GUI.

located in Effects > Transparency

 

It was created to take different exposure images and combine them into a sort of HDR image. It's pretty simple in concept so I'll give an example of how I use the plugin.

 

High, Mid, and Low exposure images:

 

On the high-exposure image, I make the bright pixels transparent so that I have detail in the dark areas. And on the low-exposure image, I make the dark pixels transparent so that I have detail in the bright areas. Then I merge those layers (just "Normal" layer blend mode) onto the mid-exposure image.

 

In the end, I have a photo with more dynamic range than what my basic phone camera could have gotten just on it's own.

Download:

SelectiveTransparency.zip

 

CodeLabs Code:

Spoiler

// Name: Selective Transparency
// Submenu: Transparency
// Author: Skysworld
// Title: Selective Transparency
// Version: 1.0
// Desc: Make pixels transparent based on their brightness 
// Keywords: transparent|transparency
// URL: https://forums.getpaint.net/profile/171721-skysworld/
// Help: https://forums.getpaint.net/profile/171721-skysworld/
#region UICode
RadioButtonControl greatLess = 0; // Effect Pixels..|Greater Than|Less Than
IntSliderControl intensity = 50; // [0,100,5] Brightness
IntSliderControl thresh = 5; // [0,10] Threshold
#endregion

protected override void OnDispose(bool disposing)
{
    if (disposing)
    {
    }
    base.OnDispose(disposing);
}

void PreRender(Surface dst, Surface src)
{
}

void Render(Surface dst, Surface src, Rectangle rect)
{
    //Loop through image's pixels
    for (int y = rect.Top; y < rect.Bottom; y++)
    {
        if (IsCancelRequested) return;
        for (int x = rect.Left; x < rect.Right; x++)
        {
            ColorBgra SrcPixel = src[x,y];
            ColorBgra CurrentPixel;
            int newAlpha = SrcPixel.A;
            
            //===============Code Start===============
            byte mostLumous;
            int pixelBrightness;
            mostLumous = SrcPixel.R;
            if (SrcPixel.G > mostLumous) {
                mostLumous = SrcPixel.G;
            }
            if (SrcPixel.B > mostLumous) {
                mostLumous = SrcPixel.B;
            }
            pixelBrightness = ((int)(mostLumous/2.55));

            //===============Code Start===============
            if (greatLess == 0) //Greater than
            {
                if (pixelBrightness > intensity) {
                newAlpha = (((int)SrcPixel.A) - Math.Abs(11-thresh)*((int)(pixelBrightness) - intensity));
                    if (newAlpha < 0) {newAlpha = 0;}
                }
            } else { //Less Than
                if (pixelBrightness < intensity) {
                    newAlpha = (((int)SrcPixel.A) - Math.Abs(11-thresh)*(intensity - ((int)(pixelBrightness))));
                    if (newAlpha < 0) {newAlpha = 0;}
                }
            }
            //===============Code End===============
            CurrentPixel = ColorBgra.FromBgra(SrcPixel.B, SrcPixel.G, SrcPixel.R, (byte)newAlpha);
            dst[x,y] = CurrentPixel;
        }
    }
}