Api Demo - .graphics(8)

//关键字：ColorMatrixColorFilter;

package com.example.android.apis.graphics;

import com.example.android.apis.R;

import android.app.Activity;
import android.content.Context;
import android.graphics.*;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;

public class ColorMatrixSample extends GraphicsActivity {
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new SampleView(this));
    }
    
    private static class SampleView extends View {
        private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);//反锯齿
        private ColorMatrix mCM = new ColorMatrix();
        private Bitmap mBitmap;
        private float mSaturation;
        private float mAngle;
        
        public SampleView(Context context) {
            super(context);
            
            mBitmap = BitmapFactory.decodeResource(context.getResources(),
                                                   R.drawable.balloons);
        }
        
        private static void setTranslate(ColorMatrix cm, float dr, float dg,
                                         float db, float da) {
            cm.set(new float[] {
                   2, 0, 0, 0, dr,
                   0, 2, 0, 0, dg,
                   0, 0, 2, 0, db,
                   0, 0, 0, 1, da });
        }
        /*
         * 第一行决定红色
         * 第二行决定绿色
         * 第三行决定蓝色，
         * 第四行决定了透明
         * 第五列是颜色的偏移量
         * 所以可以改变前4个值，按倍数改变A,R，G，B也可以改变第5列改变ARGB的固定值。
         */
        
        private static void setContrast(ColorMatrix cm, float contrast) {
            float scale = contrast + 1.f;
               float translate = (-.5f * scale + .5f) * 255.f;//浮点数运算
            cm.set(new float[] {    
                   scale, 0, 0, 0, translate,
                   0, scale, 0, 0, translate,
                   0, 0, scale, 0, translate,
                   0, 0, 0, 1, 0 });
        }
        
        private static void setContrastTranslateOnly(ColorMatrix cm, float contrast) {
            float scale = contrast + 1.f;
               float translate = (-.5f * scale + .5f) * 255.f;
            cm.set(new float[] {   // 改变第5列，线性改变颜色值；
                   1, 0, 0, 0, translate,
                   0, 1, 0, 0, translate,
                   0, 0, 1, 0, translate,
                   0, 0, 0, 1, 0 });
        }
        
        private static void setContrastScaleOnly(ColorMatrix cm, float contrast) {
            float scale = contrast + 1.f;
               float translate = (-.5f * scale + .5f) * 255.f;
            cm.set(new float[] {
                   scale, 0, 0, 0, 0,
                   0, scale, 0, 0, 0,
                   0, 0, scale, 0, 0,
                   0, 0, 0, 1, 0 });
        }
        
        @Override protected void onDraw(Canvas canvas) {
            Paint paint = mPaint;
            float x = 20;
            float y = 20;
            canvas.drawColor(Color.WHITE);
            
            ColorMatrix cm = new ColorMatrix();

            setTranslate(cm, 100, 0, 0, 0);
            paint.setColorFilter(new ColorMatrixColorFilter(cm));
            
            canvas.drawBitmap(mBitmap, x, y, paint);
            
            mAngle += 2;
            if (mAngle > 180) {
                mAngle = 0;
            }
            
            //convert our animated angle [-180...180] to a contrast value of [-1..1]
            float contrast = mAngle / 180.f;//浮点数运算
            
            setContrast(cm, contrast);
            paint.setColorFilter(new ColorMatrixColorFilter(cm));
            canvas.drawBitmap(mBitmap, x + mBitmap.getWidth() + 10, y, paint);
            
            setContrastScaleOnly(cm, contrast);
            paint.setColorFilter(new ColorMatrixColorFilter(cm));
            canvas.drawBitmap(mBitmap, x, y + mBitmap.getHeight() + 10, paint);
            
            setContrastTranslateOnly(cm, contrast);
            paint.setColorFilter(new ColorMatrixColorFilter(cm));
            canvas.drawBitmap(mBitmap, x, y + 2*(mBitmap.getHeight() + 10),
                              paint);
            
            invalidate();
        }
    }
}