Plugin don't work. Help! Source code included.

[Nitor]

Hello everyone. I'm trying to develop my first plugin. It compiles successfuly, but don’t work. Source code:

#region UICode
IntSliderControl Amount1 = 50; // [0,100] Alpha
#endregion

private byte Clamp2Byte(int iValue)
{
    if (iValue < 0) return 0;
    if (iValue > 255) return 255;
    return (byte)iValue;
}

void Render(Surface dst, Surface src, Rectangle rect)
{
    ColorBgra CurrentPixel;
    for (int y = rect.Top; y < rect.Bottom; y++)
    {
        if (IsCancelRequested) return;
        for (int x = rect.Left; x < rect.Right; x++)
        {
            CurrentPixel = src[x, y];

            double R = (int)CurrentPixel.R;
            double G = (int)CurrentPixel.G;
            double B = (int)CurrentPixel.B;

            double alpha = Amount1 / 100;

            R = (R - (255 * alpha)) / (1 - alpha);
            G = (G - (255 * alpha)) / (1 - alpha);
            B = (B - (255 * alpha)) / (1 - alpha);

            CurrentPixel = ColorBgra.FromBgra(Clamp2Byte((int), Clamp2Byte((int)G), Clamp2Byte((int)R), CurrentPixel.A);
            dst[x, y] = CurrentPixel;
        }
    }
}

Help me pls.

[BoltBait]

Please tell us what you are trying to accomplish with your plugin so we will know how to fix your algorithm.

[ReMake]

Pay attention to your formula:

R = (R - (255 * alpha)) / (1 - alpha);

It modifies the R component is too small. In the case where the Amount1 = 100 you get a black image.

[Nitor]

Ok. Blend white (with alpha) layer with colored layer and you will get new layer with new color. I want to get original colored layer with this formula: backgroundColour = (finalColour - (255 * foregroundAlpha)) / (1 - foregroundAlpha) (formula was tested by me). It get's ForegroundAlpha from Amount1 variable. After getting original colored layer it replaces finalColour to backgroundColour.

[MJW]

Change the line to:

double alpha = Amount1 / 100.0;

Otherwise, the Amount1 / 100 is done as integer arithmetic.

[Nitor]

Thank you very much!!!

[MJW]

You're most welcome. I'm glad I happened to spot that.

[toe_head2001]

On 11/22/2015 at 8:19 AM, Nitor said:

private byte Clamp2Byte(int iValue)
{
    if (iValue < 0) return 0;
    if (iValue > 255) return 255;
    return (byte)iValue;
}

...

CurrentPixel = ColorBgra.FromBgra(Clamp2Byte((int)B), Clamp2Byte((int)G), Clamp2Byte((int)R), CurrentPixel.A);

 

You don't need to write your own 'clamp to byte' function. There is already one inside paint.net. You can shave off those extra 5 lines of code.

Int32Util.ClampToByte()

Here's how it would look in your code:

CurrentPixel = ColorBgra.FromBgra(Int32Util.ClampToByte(B), Int32Util.ClampToByte(G), Int32Util.ClampToByte(R), CurrentPixel.A);