SampleWhackyColorFilter.java

package org.osmdroid.samplefragments.tilesources;

import android.graphics.ColorFilter;
import android.graphics.ColorMatrix;
import android.graphics.ColorMatrixColorFilter;

import org.osmdroid.samplefragments.BaseSampleFragment;
import org.osmdroid.tileprovider.tilesource.TileSourceFactory;
import org.osmdroid.views.overlay.TilesOverlay;

/**
 * Created by alex on 12/24/15.
 */
public class SampleWhackyColorFilter extends BaseSampleFragment {

    @Override
    public String getSampleTitle() {
        return "Whacky Color Tiles";
    }

    @Override
    public void addOverlays() {

        //p.s. there's a ton of examples here
        //http://stackoverflow.com/questions/4354939/understanding-the-use-of-colormatrix-and-colormatrixcolorfilter-to-modify-a-draw
        //http://developer.android.com/reference/android/graphics/ColorMatrix.html

        //this will make things look pinkish
        //this.mMapView.getOverlayManager().getTilesOverlay().setColorFilter(adjustHue(160));

        ColorMatrix cm = new ColorMatrix();
        float brightness =.5f;  // reduce color's by 50%. i.e. just make it darker
        cm.set(new float[] {
                brightness, 0, 0, 0, 0,    //red
                0, brightness, 0, 0, 0,    //green
                0, 0, brightness, 0, 0,    //blue
                0, 0, 0, 1, 0});    //alpha

        this.mMapView.getOverlayManager().getTilesOverlay().setColorFilter(new ColorMatrixColorFilter(cm));

        //pro tip, set the color filter to null to reset to normal viewing
    }

    /**
     * Creates a HUE adjustment ColorFilter +- 180
     * http://groups.google.com/group/android-developers/browse_thread/thread/9e215c83c3819953
     * http://gskinner.com/blog/archives/2007/12/colormatrix_cla.html
     * @param value degrees to shift the hue.
     * @return
     */
    public static ColorFilter adjustHue( float value )
    {
        ColorMatrix cm = new ColorMatrix();

        adjustHue(cm, value);

        return new ColorMatrixColorFilter(cm);
    }

    /**
     * http://groups.google.com/group/android-developers/browse_thread/thread/9e215c83c3819953
     * http://gskinner.com/blog/archives/2007/12/colormatrix_cla.html
     * @param cm
     * @param value
     */
    public static void adjustHue(ColorMatrix cm, float value)
    {
        value = cleanValue(value, 180f) / 180f * (float) Math.PI;
        if (value == 0)
        {
            return;
        }
        float cosVal = (float) Math.cos(value);
        float sinVal = (float) Math.sin(value);
        float lumR = 0.213f;
        float lumG = 0.715f;
        float lumB = 0.072f;
        float[] mat = new float[]
                {
                        lumR + cosVal * (1 - lumR) + sinVal * (-lumR), lumG + cosVal * (-lumG) + sinVal * (-lumG), lumB + cosVal * (-lumB) + sinVal * (1 - lumB), 0, 0,
                        lumR + cosVal * (-lumR) + sinVal * (0.143f), lumG + cosVal * (1 - lumG) + sinVal * (0.140f), lumB + cosVal * (-lumB) + sinVal * (-0.283f), 0, 0,
                        lumR + cosVal * (-lumR) + sinVal * (-(1 - lumR)), lumG + cosVal * (-lumG) + sinVal * (lumG), lumB + cosVal * (1 - lumB) + sinVal * (lumB), 0, 0,
                        0f, 0f, 0f, 1f, 0f
                };
        cm.postConcat(new ColorMatrix(mat));
    }

    protected static float cleanValue(float p_val, float p_limit)
    {
        return Math.min(p_limit, Math.max(-p_limit, p_val));
    }

}