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Editorial Team
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Asked: 2026-05-26T13:47:47+00:00

Hi i have two Writablebitmap , one from jpg and another from png and

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Hi i have two Writablebitmap , one from jpg and another from png and use this method to mix color in a loop:

private static Color Mix(Color from, Color to, float percent)
{
    float amountFrom = 1.0f - percent;
    return Color.FromArgb(
        (byte)(from.A * amountFrom + to.A * percent),
        (byte)(from.R * amountFrom + to.R * percent),
        (byte)(from.G * amountFrom + to.G * percent),
        (byte)(from.B * amountFrom + to.B * percent));
}

My problem is in alpha channel, my watermark effect result is bad (quality)!

Result

This is the original png.

Original Pgn

This is the original jpg.

Original Jpg

Any Help?

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1 Answer

  1. Editorial Team

    In this case you probably don’t want the result to take on any alpha from the watermark, you want it to retain 100% of the opacity of the JPEG. Instead of setting the new alpha to from.A * amountFrom + to.A * percent, just use from.A.

    Edit: In addition you want the percent to be adjusted according to the alpha of the PNG. Here’s your sample, updated:

    private static Color Mix(Color from, Color to, float percent) 
{
    float amountTo = percent * to.A / 255.0;
    float amountFrom = 1.0f - amountTo; 
    return Color.FromArgb( 
        from.A, 
        (byte)(from.R * amountFrom + to.R * amountTo), 
        (byte)(from.G * amountFrom + to.G * amountTo), 
        (byte)(from.B * amountFrom + to.B * amountTo)); 
}

    I converted this code to Python and ran your sample images through it with 0.5 percent, here’s the result:

    enter image description here

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