Android的Matrix利用數學原理實現圖片平移、旋轉等操作詳解
　　很慶幸自己的線性代數學的還可以，理解Matrix的矩陣變換完全沒有問題。Matrix矩陣實現圖片的平移旋轉等操作涉及到線性代數問題，感興趣它的具體實現的話可以參考一下上面的部落格，非常詳細，非常好。如果不想深究也可以簡單的理解為BitMap的畫素點通過某種方式（Matrix）移動了相應的位置，這樣就實現了圖片的變換。不管怎樣，先學會如何使用它就可以了。
　　注：我們所使用的Matrix變換必須有一個Bitmap基礎，因此，程式碼中需要先獲得Bitmap。

一、總體使用的簡單展示

　平移變換

//引數：移動到的位置的放大倍數
 

matrix.postTranslate(mBitmapwidth*2,mBitmapheight*2);
canvas.drawBitmap(mbitmap,matrix, mpaintline);

旋轉變換

        matrix.postRotate(180); 
        canvas.drawBitmap(mbitmap,matrix, mpaintline);

縮放變換

//引數：縮放倍數
matrix.postScale(2, 2);
canvas.drawBitmap(mbitmap,matrix, mpaintline);

錯切變換

//x軸不變，y軸進行拉伸
 

matrix.postSkew(0, 1);  
canvas.drawBitmap(mbitmap,matrix, mpaintline);

對稱（關於x軸對稱 倒影）

float[] matrix_value=new float[]{1f,0f,0f,0f,-1f,0f,0f,0f,1f};      
        matrix.setValues(matrix_value); 
        canvas.drawBitmap(mbitmap,matrix, mpaintline);

對稱（關於Y軸對稱 映象）

float[] matrix_value1=new float[]{-1f
 
,0f,0f,0f,1f,0f,0f,0f,1f};     
        matrix.setValues(matrix_value1);
        matrix.postTranslate(mBitmapwidth*2, mBitmapheight*2);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);

關於它的使用我們也是需要自定義一個class繼承View，在佈局中類名加包名進行添加布局。

二、平移變換

//原圖加平移
    matrix.reset();
        canvas.drawBitmap(mbitmap, matrix, mpaintline);

        //平移
        matrix.reset();
        matrix.postTranslate(mBitmapwidth*2,mBitmapheight*2);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);

三、旋轉變換

//原圖加旋轉加平移
matrix.reset();
        matrix.postRotate(180);
        matrix.postTranslate(mBitmapwidth*3,mBitmapheight* 2);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);

四、縮放變換

    matrix.reset();
        matrix.postScale(2, 2);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);
        matrix.reset();
        //將原圖繪製出來
        canvas.drawBitmap(mbitmap, matrix, mpaintline);

五、錯切變換

        matrix.reset();
        matrix.postSkew(0, 1);
        matrix.postTranslate(mBitmapwidth*3,mBitmapheight*3);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);

六、對稱變換

1、關於x軸對稱

    //對稱  關於x軸對稱    倒影
        matrix.reset();
        float[] matrix_value=new float[]{1f,0f,0f,0f,-1f,0f,0f,0f,1f};      
        matrix.setValues(matrix_value);
        matrix.postTranslate(0, mBitmapheight*3);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);

2、關於Y軸對稱

    //對稱  關於y軸   映象
        matrix.reset();
        float[] matrix_value1=new float[]{-1f,0f,0f,0f,1f,0f,0f,0f,1f};     
        matrix.setValues(matrix_value1);
        matrix.postTranslate(mBitmapwidth*2, mBitmapheight*2);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);

七、附完整程式碼

public class MyBitmapView extends View{
    private int width;
    private int height;
    private Paint mpaintline;
    private Bitmap mbitmap;
    private int mBitmapwidth;
    private int mBitmapheight;
    private Matrix matrix;
    public MyBitmapView(Context context) {
        super(context);
    }

    public MyBitmapView(Context context, AttributeSet attrs) {
        super(context, attrs);

        mpaintline = new Paint();
        mpaintline.setColor(Color.RED);
        mpaintline.setStrokeWidth(10);
        mpaintline.setAntiAlias(true);
        mbitmap=BitmapFactory.decodeResource(getResources(), R.drawable.yourimg);
        mBitmapwidth=mbitmap.getWidth();
        mBitmapheight=mbitmap.getHeight();
        Log.d("圖片資訊","高："+ mbitmap.getHeight()+"寬："+mbitmap.getWidth());
        matrix=new Matrix();
    }

    @Override
    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);
//  canvas.drawBitmap(mbitmap, 20, 20, mpaintline);
        //放縮
        matrix.reset();
        matrix.postScale(2, 2);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);
        matrix.reset();
        canvas.drawBitmap(mbitmap, matrix, mpaintline);

        //平移
        matrix.reset();
        matrix.postTranslate(mBitmapwidth*2,mBitmapheight*2);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);

        //旋轉
        matrix.reset();
        matrix.postRotate(180);
        matrix.postTranslate(mBitmapwidth*3,mBitmapheight* 2);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);
        //錯切
        matrix.reset();
        matrix.postSkew(0, 1);
        matrix.postTranslate(mBitmapwidth*3,mBitmapheight*3);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);


        //對稱  關於x軸對稱    倒影
        matrix.reset();
        float[] matrix_value=new float[]{1f,0f,0f,0f,-1f,0f,0f,0f,1f};      
        matrix.setValues(matrix_value);
        matrix.postTranslate(0, mBitmapheight*3);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);

        //對稱  關於y軸   映象
        matrix.reset();
        float[] matrix_value1=new float[]{-1f,0f,0f,0f,1f,0f,0f,0f,1f};     
        matrix.setValues(matrix_value1);
        matrix.postTranslate(mBitmapwidth*2, mBitmapheight*2);
        canvas.drawBitmap(mbitmap,matrix, mpaintline);

    }

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

        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        width = getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec);
        height = getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec);
    }
}