Android图形图画学习(10)——AlphaBitmap

private static class SampleView extends View {        private Bitmap mBitmap;        private Bitmap mBitmap2;        private Bitmap mBitmap3;        private Shader mShader;        private static void drawIntoBitmap(Bitmap bm) {       //正如在图形图画学习(1)中提到的，画图有两种，一种是在空白画图上作画，一种是在已知的一张Bitmap上作画。这里展示了如何在一张Bitmap上作画            float x = bm.getWidth();            float y = bm.getHeight();            Canvas c = new Canvas(bm);            Paint p = new Paint();               //组成图画的基本单元由画笔决定，例如，透明度，色彩，抖动等等。            p.setAntiAlias(true);            p.setAlpha(0x80);            c.drawCircle(x/2, y/2, x/2, p);                              //Canvas类是画图工具类，这是一个画圆工具            p.setAlpha(0x30);            p.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));            p.setTextSize(60);            p.setTextAlign(Paint.Align.CENTER);            Paint.FontMetrics fm = p.getFontMetrics();            c.drawText("Alpha", x/2, (y-fm.ascent)/2, p);                       //这是一个绘制文字的工具        }        public SampleView(Context context) {            super(context);            setFocusable(true);            InputStream is = context.getResources().openRawResource(R.drawable.app_sample_code);            mBitmap = BitmapFactory.decodeStream(is);            mBitmap2 = mBitmap.extractAlpha();            mBitmap3 = Bitmap.createBitmap(200, 200, Bitmap.Config.ALPHA_8);            drawIntoBitmap(mBitmap3);            mShader = new LinearGradient(0, 0, 100, 70, new int[] {                      //着色器实现了渐变色彩，仍然交给画笔处理                                         Color.RED, Color.GREEN, Color.BLUE },                                         null, Shader.TileMode.MIRROR);        }        @Override protected void onDraw(Canvas canvas) {            canvas.drawColor(Color.WHITE);            Paint p = new Paint();            float y = 10;            p.setColor(Color.RED);            canvas.drawBitmap(mBitmap, 10, y, p);//最终位图依然依托于View的onDraw()回调交由系统画布绘制出来            y += mBitmap.getHeight() + 10;            canvas.drawBitmap(mBitmap2, 10, y, p);            y += mBitmap2.getHeight() + 10;            p.setShader(mShader);            canvas.drawBitmap(mBitmap3, 10, y, p);        }    }
更多相关文章

随机推荐
