canvas 相关

流程

使用

1. 要素
   • 保存像素的bitmgap: A Bitmap to hold the pixeles
   • 画笔Paint: A Paint to describe the colors and styles for drawing
   • 绘制图像: A drawing primitive (e.g. Rect, Path, text, Bitmap)
   • canvas画布，用来在Bitmap上使用Paint绘制内容:A Canvas to host the draw calls (writing into the bitmap)
2. Summary
   • Canvas.EdgeType

   • Canvas.VertexMode

   • Canvas()
   • Canvas(Bitmap bitmap)
3. Method
   • clipPath(Path path, Region.Op op) : 裁剪为指定的路径
   • clipPath(Path path) : Intersect the current clip with eht specified path 横切为指定路径
   • clipRect ：裁剪为指定矩形
   • clipRegion : >= API 21 deprecated

   • concat(Matrix matrix) : preconcat the current matrix with the specified matrix

   • drawARGB ：使用指定颜色填充canvas bitmap
   • drawArc : 绘制弧，扇形，弓形等
   • drawBitmap
   • drawCircle : 绘制圆或圈
   • drawLine : 绘制线
   • drawOval : 绘制椭圆
   • drawRect
   • drawText
   • drawRoundRect
   • drawVertices : 绘制顶点

   • drawPicture : 绘制图片

   • getMatrix
   • setMatrix
   • getDensity
   • setDensity
   • getBitmap
   • setBitmap
   • getDrawFilteg

   • setDrawFilter

   • restore :
   • save

   • saveLayer

   • rotate
   • scale
   • translate
   • skew(扭曲)

ColorFilter

A color filter can be used with a Paint to modify th color of each pixel drawn with that paint. Abstract class

ColorMatrix

ComposePathEffect ComposePathEffect (PathEffect outerpe, PathEffect innerpe) Construct a PathEffect whose effect is to apply first the inner effect and the the outer pathEffect (e.g. outer(inner(path))).

Outline : Defines a simple shape, used for bounding graphical regions. `

Shader

• getLocalMatrix(Matrix localM)
• setLocalMatrix(Matrix localM)

BitmapShader to draw a bitmap as a texture.

可以通过设置till mode, 重复使用 BitmapShader(Bitmap bitmap, Shader.TileMode tileX, Shader.TileMode tileY);

ComposeGradient 结合Xfermode, 其他两个shader的组合

• ComposeShader(Shader shaderA, Shader shaderB, Xfermode mode)
• ComposeShader(Shader shaderA, Shader shaderB, PorterDuff.Mode mode)
• shaderA 的颜色作为”dst”模式, shaderB “src”
• Xfermode: 两个着色器与颜色结合的模式。如果为null,则为SRC_OVER。
• PorterDuff.Mode: PorterDuff结合的着色器。

LinearGradient

• LinearGradient(float x0, float y0, float x1, float y1, int[] colors, float[] positions, Shader.TileMode tile)
• colors 沿渐变线的颜色分布，postions 每个相应颜色的颜色数组。
• LinearGradient(float x0, float y0, float x1, float y1, int color0开始的颜色, int color1结束的颜色, Shader.TileMode tile)

RadialGradient

• RadialGradient(float centerX, float centerY, float radius, int[] colors, float[] stops, Shader.TileMode tileMode)
• colors 沿圆中心到边缘的颜色分布，stops 可以为null，[0,1f],对应颜色数组。
• RadialGradient(float centerX, float centerY, float radius, int centerColor, int edgeColor, Shader.TileMode tileMode)

SweepGradient 梯度渲染

• SweepGradient(float cx, float cy, int[] colors, float[] positions)
• SweepGradient(float cx, float cy, int color0, int color1)