src/com/pheelicks/visualizer/renderer/BarGraphRenderer.java


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/**
 * Copyright 2011, Felix Palmer
 *
 * Licensed under the MIT license:
 * http://creativecommons.org/licenses/MIT/
 */
package com.pheelicks.visualizer.renderer;

import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;

import com.pheelicks.visualizer.AudioData;
import com.pheelicks.visualizer.FFTData;

public class BarGraphRenderer extends Renderer
{
  private int mDivisions;
  private Paint mPaint;
  private boolean mTop;

  /**
   * Renders the FFT data as a series of lines, in histogram form
   * @param canvas
   * @param divisions - must be a power of 2. Controls how many lines to draw
   * @param paint - Paint to draw lines with
   * @param top - whether to draw the lines at the top of the canvas, or the bottom
   */
  public BarGraphRenderer(Canvas canvas,
                          int divisions,
                          Paint paint,
                          boolean top)
  {
    super(canvas);
    mDivisions = divisions;
    mPaint = paint;
    mTop = top;
  }

  @Override
  public void onRender(AudioData data, Rect rect)
  {
    // Do nothing, we only display FFT data
  }

  @Override
  public void onRender(FFTData data, Rect rect)
  {
    for (int i = 0; i < data.bytes.length / mDivisions; i++) {
      mFFTPoints[i * 4] = i * 4 * mDivisions;
      mFFTPoints[i * 4 + 2] = i * 4 * mDivisions;
      byte rfk = data.bytes[mDivisions * i];
      byte ifk = data.bytes[mDivisions * i + 1];
      float magnitude = (rfk * rfk + ifk * ifk);
      int dbValue = (int) (10 * Math.log10(magnitude));

      if(mTop)
      {
        mFFTPoints[i * 4 + 1] = 0;
        mFFTPoints[i * 4 + 3] = (dbValue * 2 - 10);
      }
      else
      {
        mFFTPoints[i * 4 + 1] = rect.height();
        mFFTPoints[i * 4 + 3] = rect.height() - (dbValue * 2 - 10);
      }
    }

    mCanvas.drawLines(mFFTPoints, mPaint);
  }
}