Watercolor effect

On Friday I found this amazing work from Stamen where they convert in real time an OpenStreetMap map into a wonderful watercolor like drawing. Check it out here !

I really love the result, it’s absolutely gorgeous. Lucky me, they give a few headlights on the whole process on their blog : http://content.stamen.com/watercolor_process

So I decided to create and bench the same effect in Flash. No Stage3D this time, only bitmap manipulation.

First, the demo :streaming film Zoolander 2 2016

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First slider change the threshold sensitivity
Second slider change the perlin noise alpha
Use checkboxes to disable the shadows or to view the used mask

Right now the demo is a bit heavy. Almost no optimization was done, and I wonder if some of the computation could be done using pixel bender.

You can find every step image on the Stamen blog post, so I won’t detail them here, but here is the effect code. Feel free to go back and fourth between the two blog to see the filter in action step by step.

     private function filterColor(colorToFilter:uint, textureToApply:Bitmap, sensitivity:int = 90):void {
     var msk:Bitmap = new Bitmap(new BitmapData(_mask.width, _mask.height, true, 0xFF000000));
      // _mask is a generated bitmap we get using a background color, the textfield, and the two vector assets.
      // You can see it by selected the "show mask" checkbox

     msk.bitmapData.threshold(_mask.bitmapData, _mask.getBounds(this), new Point(0,0), "==", colorToFilter, 0xFFFFFFFF, 0xFFFFFFFF, false);
     // first threshold separate the given color, for instance pink for the text

     msk.bitmapData.applyFilter(msk.bitmapData, _mask.getBounds(this), new Point(0,0), new BlurFilter(4.5, 4.5, 2));
     msk.bitmapData.draw(_noise, null, new ColorTransform(.5, .5, .5, _slAlpha.value), BlendMode.NORMAL, null, true);
     // Blur then apply a "noise". _noise is a simple perlin noise bitmap generated on app initialisation We use the same for every layers

     msk.bitmapData.threshold(msk.bitmapData, _mask.getBounds(this), new Point(0,0), "", sensitivity, 0xFFFFFFFF, 0x000000FF);
     // those threshold give us a black and white mask wich is a bit deformed by the noise and the blur filter.
     // The higher the sensitivity (which is actually just the color limit of the threshold from 0 to 255), the more the mask shrink, leaving some white space between layers)

     msk.bitmapData.applyFilter(msk.bitmapData, _mask.getBounds(this), new Point(0,0), new BlurFilter(2, 2, 3));
     msk.bitmapData.threshold(msk.bitmapData, _mask.getBounds(this), new Point(0,0), "<=", 0x66, 0xFF000000, 0x000000FF);
     // New blur / threshold operation to round a little bit the previous mask

     msk.bitmapData.applyFilter(msk.bitmapData, _mask.getBounds(this), new Point(0,0), new BlurFilter(1.2, 1.2, 1));
     // small blur to antialiase the mask

          var shadow:BitmapData = msk.bitmapData.clone();
          shadow.applyFilter(shadow, _mask.getBounds(this), new Point(0,0), new BlurFilter(5, 5, 3));
          shadow.copyChannel(msk.bitmapData, _mask.getBounds(this), new Point(0,0), BitmapDataChannel.RED, BitmapDataChannel.ALPHA);
     // the inner shadow is just the same mask blured again, then cut into by copying the unblurred mask red channel into the blurred mask alpha channel.

     var bmp:Bitmap = new Bitmap();
     bmp.bitmapData = textureToApply.bitmapData.clone();

     bmp.bitmapData.copyChannel(msk.bitmapData, _mask.getBounds(this), new Point(0,0), BitmapDataChannel.RED, BitmapDataChannel.ALPHA);
     // Copy the mask red channel (could have been green or blue since we are working in greyscale) into texture alpha channel.

     if(_useShadow.selected) bmp.bitmapData.draw(shadow, null, new ColorTransform(1, 1, 1, .4), BlendMode.MULTIPLY, null, true);
     // Eventually draw the shadow bitmap onto the texture.


That’s it ! Not as beautiful as the Stamen work, but right now I’m satisfied with the result.

I’m not giving the whole code since it’s embedded into the Agency Framework, so I would have to upload a lot of classes for a single effect, but you can try it by yourself really easily.

Credit goes for Stamen for the idea, and for Stamen again for those wonderful texture I used