fabric类的继承体系

StaticCanvas
    Canvas

Object
    Triangle
    Circle
    Ellipse
    Image
    Line
    Path
    Rect
    Polyline
        Polygon
    Group
        ActiveSelection
    Text
        IText
            Textbox

BaseBrush
    PatternBrush
    PencilBrush

SprayBrush
Point
CircleBrush
Gradient
Color
Intersection
Pattern
Shadow

BaseFilter
    Blur
    Brightness
    ColorMatrix
    Contrast
    Convolute
    BlendColor
    BlendImage
    Gamma
    Grayscale
    HueRotation
    Invert
    Noise
    Pixelate
    RemoveColor
    Resize
    Saturation
    Vibrance