Hydra filters

I’ve been mucking about with others’ Hydra examples since I saw the movies of it at max. Basically its a language based on C designed to perform image processing tasks. Eventually Hydra will be implemented into after effects, photoshop and a subset of the specs into the flash player.

Here are the results of my experiments:

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1. MASK

The following code takes two images, gets the grayscale of the mask and then the alpha of the base image to the grayscale.

kernel mask{void evaluatePixel(in image4 src,in image4 mask, out pixel4 dst)

{

float4 maskImage = sampleNearest(mask, outCoord());

float4 outputImage = sampleNearest(src, outCoord());

float grayscale = (maskImage.r + maskImage.g + maskImage.b) / 3.0;

outputImage.a = grayscale;

dst = outputImage;

}

}

The following two input images (the hello as the mask)

Produce:

Grey is the default background colour so the image is transparent over that.

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2: WIGGLE

I also created a wiggle filter

kernel morph

{parameter float xangle<

    minValue: 0.0;

    maxValue:10.0;

    defaultValue:5.0;

>;

parameter float yangle<

    minValue: 0.0;

    maxValue:10.0;

    defaultValue:0.0;

>;

void evaluatePixel(in image4 src, out pixel4 dst)

    {

        float2 coord = outCoord();

        float xcoord = coord.x - sin(coord.y)*xangle;

        float ycoord = coord.y - sin(coord.x)*yangle;

        dst = sampleNearest(src,float2(xcoord,ycoord));

    }

}

This filter takes inputs of the wiggle size of the x and y and produces the following examples:

Wiggle on both the x and the y

a wiggle just on the x

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3. FLIP
And an flip filter. In the documentation there is a referenceFrame parameter to get the bounds of the input image. However after experimenting with it I couldn’t get it to work. I posted on the adobe forums and found out that it has not been implemented yet, so having a parameter with the width will have to do for now.

kernel flip

   parameter float width< minValue: 100.0;
        maxValue: 200.0;
        defaultValue:500.0;
        description: "Width of image";
   >;

    void  evaluatePixel(in image4 src, out pixel4 dst)
    {
        float2 coord = outCoord();
        float2 newcoord = float2(width-coord.x,coord.y);
        dst = sampleNearest(src,newcoord);
    }
}