ImageDraw

ImageDraw module provides support for simple 2D graphics. The graphics commands support shape drawing and text annotation.

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• An image can be considered to be a two-dimensional array of pixels (picture elements). A pixel is the smallest dot of color being supported,

• The two-dimensional coordinate system used by ImageDraw has the origin in the upper left corner of the image.

• The Pillow color scheme we use is RGB. The module ImageColor provides color RGB representation and support.

• The acceptable fonts for text annotations are bitmap, OpenType, or TrueType.

• Many of the drawing commands require a bounding box parameter that specifies the area on the image to which the command is to be applied. A bounding box is specified by giving the upper left and lower right corners of the rectangular canvas subregion being draw on. There are are two supported bounding box representations.

Suppose coordinates (x0, y0 and (x1, y1) are respectively the upper left and lower right box coordimates of interest. The bounding box representation for those two corners is [ (xo, y0), (x1, y1) ].

• A sequence of coordinates can be represented as [ (xo, y0), (x1, y1), ... ].

• Some drawing commands require angle values. The origin angle is that of the little hand for analog clock whose time at 3 o'clock.

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Canvas

• A Pillow drawable surface (i.e., a canvas) of an Image is an ImageDraw.

• ImageDraw.Draw( im ) returns a drawable canvas representation of Image parameter im. The background of the canvas is the im image.

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Drawing

• Suppose below canvas is a drawable image.

• canvas.line( xy, fill=None, width=0 )

• Draws a line from the upper left to lower right corners of bounding box xy on canvas. The line is filled using color fill. Parameters fill and width are optional with default values respectively of None and 0.

• canvas.rectangle( xy, fill=None, outline=None )

• Draws the rectangle given bounding box xy on canvas. The shape is filled using color fill and the perimeter in color outline. Parameters fill and outline are optional with default values None.

• canvas.ellipse( xy, fill=None, outline=None )

• Draws the ellipse surrounded by bounding box xy on canvas. The shape is filled using color fill and the perimeter in color outline. Parameters fill and outline are optional with default values None.

• canvas.point( seq, fill=None )

• Draws pixels (points) at coordinate sequence locations seq on canvas. The pixels are filled using color fill. Parameter fill is optional with default value None.

• canvas.polygon( seq, fill=None, outline=None )

• Draws a polygon connecting with straight lines the coordinate sequence locations seq on canvas. The first and last coordinates in seq are also connected by a straight-line. The shape is filled using color fill and the perimeter in color outline. Parameters fill and outline are optional with default values None.

• canvas.arc( xy, sa, ea, fill=None )

• Draws an arc within bounding box xy on canvas. The arc outline has starting angle sa and ending angle ea. The shape is drawn using color fill. Parameter fill is optional with default value None.

• canvas.chord( xy, sa, ea, fill=None, outline=None )

• Draws a chord within bounding box xy on canvas. The chord arc has starting angle sa and ending angle ea and the arc endpoints are connected by a straight-line. The shape is filled using color fill and the perimeter in color outline. Parameters fill and outline are optional with default values None.

• canvas.pieslice( xy, sa, ea, fill=None, outline=None )

• Draws a pie slice within bounding box xy on canvas. The pie slice arc has starting angle sa and ending angle ea. Lines are drawn from the arc endpoints to the center of the bounding box. The shape is filled using color fill and the perimeter in color outline. Parameters fill and outline are optional with default values None.

• canvas.text( loc, s, fill=None, font=None, anchor=None, spacing=0, align='left')

• Writes string s at coordinate loc on canvas. The text is written using color fill in font font with line spacing space and alignment align. Parameters fill, font, spacing, and align are optional with default values respectively of None, None, 0, and left. The possible values for align are 'left', 'center' and 'right'.

 

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© 2019 Jim Cohoon

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