[Android] Graphics: Drawable & Images & Canvas

1. Docs
   
   • Drawable Resources
     http://developer.android.com/guide/topics/resources/drawable-resource.html
   • 2D Graphics
     http://developer.android.com/guide/topics/graphics/2d-graphics.html
   • Toll to Draw 9-patch Drawable
     http://developer.android.com/guide/developing/tools/draw9patch.html
     
   • xxx
     
2. Packages
   
   • android.graphics
   • android.graphics.drawable
   • android.graphics.drawable.shapes
3. Classes
   
   • Drawable
     A Drawable is a general abstraction for "something that can be drawn.". Unlike a View, a Drawable does not have any facility to receive events or otherwise interact with the user. Drawables may take a variety of forms:
     
     • Bitmap
     • Nine Patch
     • Shape
     • Layers
     • States
     • Levels
     • Scale
     
     Some sub-classes
     
     • ColorDrawable
       A specialized Drawable that fills the Canvas with a specified color.
       
     • ClipDrawable
       A Drawable that clips another Drawable based on this Drawable's current level value.
       
     • BitmapDrawable
       A Drawable that wraps a bitmap and can be tiled, stretched, or aligned.
       
     • AnimationDrawable
       An object used to create frame-by-frame animations, defined by a series of Drawable objects, which can be used as a View object's background.
       
     • ShapeDrawable
       Use Shape: such as ArcShape, RectShape, RoundRectShape, PathShape, OvalShape.
       
     • ......
       
     • xxx
       
     
     xxx
     
   • Bitmap
     
     • Get attributes of Bitmap
     • Create Bitmap
     • Clip Bitmap
       
     • xxx
       
   • BitmapFactory
     Creates Bitmap objects from various sources, including files, streams, and byte-arrays. ie:
     Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.xxx);
     
   • BitmapRegionDecoder
     Decode a rectangle region from an image. BitmapRegionDecoder is particularly useful when an original image is large and you only need parts of the image.
     
   • NinePatch
     A NinePatch drawable is a standard PNG image that includes an extra 1-pixel-wide border, the border is used to define the stretchable and static areas of the image.
     Draw a bitmap in nine sections (9-Patch).
     
   • Camera
     Used to compute 3D transformations: rotate, move, translate.
     
   • Movie
     
     • Load Move from file, input stream, byte array
     • Draw movie on Canvas
     • Get arrtibutes
       
   • Paint
     The Paint class holds the style and color information about how to draw geometries, text and bitmaps on Canvas.
     
   • Canvas
     The Canvas class holds the "draw" calls. To draw something, you need 4 basic components: A Bitmap to hold the pixels, a Canvas to host the draw calls (writing into the bitmap), a drawing primitive (e.g. Rect, Path, text, Bitmap), and a paint (to describe the colors and styles for the drawing).
     
     • get/set attributes
     • scale/rotate/translate
     • draw:
       
       1. color/image/picture
       2. point/line/rect
       3. text
     • clip
       
       1. path
       2. rect
       3. region
     • xxx
       
   • Color
     
     • Color
       
     1. Contains pre-defined colors: GREEN, GRAY, xxx
     2. Return the alpha/red/green/blue component of a color int
     3. Return a color-int from alpha, red, green, blue components.
     • ColorMatrix
       5x4 matrix for transforming the color+alpha components. The matrix is stored in a single array.
       
       Used by: Paint <- ColorFilter <- ColorMatrixFilter <- ColorMatrix
       
     • xxx
       
   • Path
     The Path class encapsulates compound (multiple contour) geometric paths consisting of straight line segments, quadratic curves, and cubic curves. It can be drawn with canvas.drawPath(path, paint), either filled or stroked (based on the paint's Style), or it can be used for clipping or to draw text on a path.
     
   • Point (PointF - for float coordinates)
     
   • Rect
     
   • ImageView
     
     • Set image
       Bitmap bmp = xxxx;
       ImageView imgView = xxx;
       imgView.setImageBitmap(bmp);
   • xxx
     
4. xxx