Paint 画笔的高级技能
渲染 Shader:
BitmapShader位图的图象渲染器
LinearGradient线性渲染
RadialGradient环形渲染
SweepGradient梯度渲染（扫描渲染）
ComposeShader组合渲染
可以绘制图片、颜色块、文字
canvas.drawCircle()
canvas.drawRect()
canvas.drawOval()
public class LinearGradientTextView extends android.support.v7.widget.AppCompatTextView { private TextPaint paint; private LinearGradient linearGradient; private Matrix matrix; private float translateX; private float deltaX = 20; public LinearGradientTextView(Context context) { super(context);
} public LinearGradientTextView(Context context,
@Nullable AttributeSet attrs) { super(context, attrs);
} @Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh);
paint = getPaint(); //GradientSize=两个文字的大小
String text = getText().toString(); float textWidth = paint.measureText(text); int gradientSize = (int) (3 * textWidth / text.length());
linearGradient = new LinearGradient(-gradientSize, 0, 0, 0, new int[]{0x22ffffff, 0xffffffff, 0x22ffffff}, new float[]{0, 0.5f, 1}, TileMode.CLAMP);//边缘融合
paint.setShader(linearGradient);
matrix = new Matrix();
} @Override
protected void onDraw(Canvas canvas) { super.onDraw(canvas); float textWidth = getPaint().measureText(getText().toString());
translateX += deltaX; if(translateX > textWidth + 1|| translateX < 1){
deltaX = -deltaX;
}// matrix.setScale(sx, sy)
//动画平移
matrix.setTranslate(translateX, 0);
linearGradient.setLocalMatrix(matrix);
postInvalidateDelayed(50);
}
}public class MyGradientView extends View { private Bitmap bitmap; private Paint paint; private BitmapShader bitmapShader; private int width; private int height; private int[] colors = {Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW}; private RadialGradient radialGradient; private SweepGradient sweepGradient; //组合渲染
private ComposeShader composeShader; public MyGradientView(Context context) { super(context);
bitmap = ((BitmapDrawable) getResources().getDrawable(R.drawable.fengjing)).getBitmap();
paint = new Paint();
width = bitmap.getWidth();
height = bitmap.getHeight();
} public MyGradientView(Context context,
@Nullable AttributeSet attrs,
Bitmap bitmap) { super(context, attrs); this.bitmap = bitmap;
} public MyGradientView(Context context,
@Nullable AttributeSet attrs, int defStyleAttr,
Bitmap bitmap) { super(context, attrs, defStyleAttr); this.bitmap = bitmap;
} /**
*
* @param canvas
*/
@Override
protected void onDraw(Canvas canvas) { super.onDraw(canvas);
canvas.drawColor(Color.WHITE); //canvas.drawBitmap(bitmap, 0, 0, paint);
/**
* TileMode.CLAMP 拉伸最后一个像素去铺满剩下的地方
* TileMode.MIRROR 通过镜像翻转铺满剩下的地方
* TileMode.REPEAT 重复图片填充整个画面(电脑设置壁纸)
*/
bitmapShader = new BitmapShader(bitmap, TileMode.REPEAT, TileMode.REPEAT); // bitmapShader = new BitmapShader(bitmap, TileMode.CLAMP, TileMode.CLAMP);
paint.setShader(bitmapShader);
paint.setAntiAlias(true); //canvas.drawRect(new Rect(0, 0, 800, 800), paint);
//设置像素矩阵，来调整大小，为了解决宽高不一致的问题// float scale = Math.max(width, height) * 1.0f / Math.min(width, height);// Matrix matrix = new Matrix();// matrix.setScale(scale, scale);//缩放比例// bitmapShader.setLocalMatrix(matrix);
// canvas.drawRect(new Rect(0, 0, 800, 800), paint);
//canvas.drawCircle(width/2,width/2, width/2,paint);
// canvas.drawCircle(Math.max(width, height) / 2f,
// scale * Math.max(width, height) / 2f, Math.max(width, height) / 2f, paint);
//canvas.drawOval(new RectF(0, 0, width, height * 1.5f), paint);
// canvas.drawOval(new RectF(0,0,width,width),paint);
//通过shapeDrawable也可以实现// ShapeDrawable shapeDrawable =new ShapeDrawable(new OvalShape());// shapeDrawable.getPaint().setShader(bitmapShader);// shapeDrawable.setBounds(0,0,width,width);// shapeDrawable.draw(canvas);
/**
* 线性渐变
* x0，y0 起始点
* x1，y1 结束点
* int[] colors 中间依次要出现的颜色
* float[] positions 数组大小跟colors数组一样大，中间依次摆放的几个颜色分别放置在那个位置上(参考比例从左往右)
* title
*
*/// LinearGradient linearGradient = new LinearGradient(0, 0, 400, 400, colors, null,// TileMode.REPEAT);// paint.setShader(linearGradient);// canvas.drawRect(0,0,400,400,paint);// //环形渲染// radialGradient = new RadialGradient(300,300,100,colors,null,TileMode.REPEAT);// paint.setShader(radialGradient);// canvas.drawCircle(300,300,300,paint);
//梯度渲染// sweepGradient = new SweepGradient(300, 300, colors, null);// paint.setShader(sweepGradient);// canvas.drawCircle(300, 300, 300, paint);
//组合渲染
LinearGradient linearGradient = new LinearGradient(0, 0, 400, 400, colors, null,
TileMode.REPEAT);
composeShader = new ComposeShader(linearGradient, bitmapShader, PorterDuff.Mode.SRC_OVER);
paint.setShader(composeShader);
canvas.drawRect(0, 0, 800, 1000, paint);
}
}public class ZoomImageView extends View { //放大倍数
private static final int FACTOR = 3; private static final int RADIUS = 100; public Bitmap bitmap; private ShapeDrawable drawable; private Matrix matrix = new Matrix(); public ZoomImageView(Context context) { super(context);
bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.beauty);
Bitmap bmp = bitmap;
bmp = Bitmap
.createScaledBitmap(bmp, bmp.getWidth() * FACTOR, bmp.getHeight() * FACTOR, true); //制作一个圆形的图片(放大的局部)，盖在canvas上
BitmapShader shader = new BitmapShader(bmp, TileMode.CLAMP, TileMode.CLAMP);
drawable = new ShapeDrawable(new OvalShape());
drawable.getPaint().setShader(shader); //切出矩形区域----用于绘制圆（内切圆）
drawable.setBounds(0, 0, RADIUS * 2, RADIUS * 2);
} @Override
protected void onDraw(Canvas canvas) { super.onDraw(canvas);
canvas.drawBitmap(bitmap, 0, 0, null); //画制作好的圆形图片
drawable.draw(canvas);
} @Override
public boolean onTouchEvent(MotionEvent event) { int x = (int) event.getX(); int y = (int) event.getY();
matrix.setTranslate(RADIUS - x * FACTOR, RADIUS - y * FACTOR);
drawable.getPaint().getShader().setLocalMatrix(matrix);
drawable.setBounds(x - RADIUS, y - RADIUS, x + RADIUS, y + RADIUS); //手指按下才进行缩放
postInvalidate(); return super.onTouchEvent(event);
}
}
作者：香沙小熊
链接：https://www.jianshu.com/p/160fca0af672
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