app/src/com/google/android/DemoKit/ColorWheel.java

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.android.DemoKit;

import android.content.Context;
import android.graphics.*;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;


/* This class was masterfully pilfered, Carmen-Sandiego style, from our awesome sample app
 * ApiDemos.  To see how it looks as a dialog, check out:
 * http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/graphics/ColorPickerDialog.html
 *
 */

  public class ColorWheel extends View {
      public interface OnColorChangedListener {
          void colorChanged(int color);
      }

      /*
      */

      private OnColorChangedListener mListener;

      private int mInitialColor;

      private Paint mPaint;
      private Paint mCenterPaint;
      private final int[] mColors;

      public void setOnColorChangedListener(OnColorChangedListener l) {
          mListener = l;
      }


      public ColorWheel(Context c, AttributeSet attributes) {

          super(c, attributes);

          mColors = new int[] {
              0xFFFF0000, 0xFFFF00FF, 0xFF0000FF, 0xFF00FFFF, 0xFF00FF00,
              0xFFFFFF00, 0xFFFF0000
          };
          Shader s = new SweepGradient(0, 0, mColors, null);

          mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
          mPaint.setShader(s);
          mPaint.setStyle(Paint.Style.STROKE);
          mPaint.setStrokeWidth(32);

          mCenterPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
          mCenterPaint.setColor(0);
          mCenterPaint.setStrokeWidth(5);
      }



      private boolean mTrackingCenter;
      private boolean mHighlightCenter;

      @Override
      protected void onDraw(Canvas canvas) {
          super.onDraw(canvas);
          float r = CENTER_X - mPaint.getStrokeWidth()*0.5f;

          canvas.translate(CENTER_X, CENTER_X);

          canvas.drawOval(new RectF(-r, -r, r, r), mPaint);
          canvas.drawCircle(0, 0, CENTER_RADIUS, mCenterPaint);

          if (mTrackingCenter) {
              int c = mCenterPaint.getColor();
              mCenterPaint.setStyle(Paint.Style.STROKE);

              if (mHighlightCenter) {
                  mCenterPaint.setAlpha(0xFF);
              } else {
                  mCenterPaint.setAlpha(0x80);
              }
              canvas.drawCircle(0, 0,
                                CENTER_RADIUS + mCenterPaint.getStrokeWidth(),
                                mCenterPaint);

              mCenterPaint.setStyle(Paint.Style.FILL);
              mCenterPaint.setColor(c);
          }
      }

      @Override
      protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

          setMeasuredDimension(CENTER_X*2, CENTER_Y*2);
      }

      private static final int CENTER_X = 200;
      private static final int CENTER_Y = 200;
      private static final int CENTER_RADIUS = 64;

      private int floatToByte(float x) {
          int n = java.lang.Math.round(x);
          return n;
      }
      private int pinToByte(int n) {
          if (n < 0) {
              n = 0;
          } else if (n > 255) {
              n = 255;
          }
          return n;
      }

      private int ave(int s, int d, float p) {
          return s + java.lang.Math.round(p * (d - s));
      }

      private int interpColor(int colors[], float unit) {
          if (unit <= 0) {
              return colors[0];
          }
          if (unit >= 1) {
              return colors[colors.length - 1];
          }

          float p = unit * (colors.length - 1);
          int i = (int)p;
          p -= i;

          // now p is just the fractional part [0...1) and i is the index
          int c0 = colors[i];
          int c1 = colors[i+1];
          int a = ave(Color.alpha(c0), Color.alpha(c1), p);
          int r = ave(Color.red(c0), Color.red(c1), p);
          int g = ave(Color.green(c0), Color.green(c1), p);
          int b = ave(Color.blue(c0), Color.blue(c1), p);

          return Color.argb(a, r, g, b);
      }

      private int rotateColor(int color, float rad) {
          float deg = rad * 180 / 3.1415927f;
          int r = Color.red(color);
          int g = Color.green(color);
          int b = Color.blue(color);

          ColorMatrix cm = new ColorMatrix();
          ColorMatrix tmp = new ColorMatrix();

          cm.setRGB2YUV();
          tmp.setRotate(0, deg);
          cm.postConcat(tmp);
          tmp.setYUV2RGB();
          cm.postConcat(tmp);

          final float[] a = cm.getArray();

          int ir = floatToByte(a[0] * r +  a[1] * g +  a[2] * b);
          int ig = floatToByte(a[5] * r +  a[6] * g +  a[7] * b);
          int ib = floatToByte(a[10] * r + a[11] * g + a[12] * b);

          return Color.argb(Color.alpha(color), pinToByte(ir),
                            pinToByte(ig), pinToByte(ib));
      }

      private static final float PI = 3.1415926f;

      @Override
      public boolean onTouchEvent(MotionEvent event) {
          float x = event.getX() - CENTER_X;
          float y = event.getY() - CENTER_Y;
          boolean inCenter = java.lang.Math.sqrt(x*x + y*y) <= CENTER_RADIUS;

          switch (event.getAction()) {
              case MotionEvent.ACTION_DOWN:
                  mTrackingCenter = inCenter;
                  if (inCenter) {
                      mHighlightCenter = true;
                      invalidate();
                      break;
                  }
              case MotionEvent.ACTION_MOVE:
                  if (mTrackingCenter) {
                      if (mHighlightCenter != inCenter) {
                          mHighlightCenter = inCenter;
                          invalidate();
                      }
                  } else {
                      float angle = (float)java.lang.Math.atan2(y, x);
                      // need to turn angle [-PI ... PI] into unit [0....1]
                      float unit = angle/(2*PI);
                      if (unit < 0) {
                          unit += 1;
                      }
                      mCenterPaint.setColor(interpColor(mColors, unit));
                      invalidate();
                      mListener.colorChanged(mCenterPaint.getColor());
                  }
                  break;
              case MotionEvent.ACTION_UP:
                  if (mTrackingCenter) {
                      if (inCenter) {
                          mListener.colorChanged(mCenterPaint.getColor());
                      }
                      mListener.colorChanged(0);
                      // mListener.colorChanged(mCenterPaint.getColor());
                      mTrackingCenter = false;    // so we draw w/o halo
                      invalidate();
                  }
                  break;
          }
          return true;
      }
  }