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PyCairo – Drawing different type of line caps

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  • Last Updated : 23 Jan, 2022
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In this article, we will learn how we can draw different line caps types using PyCairo in python. The line caps are endpoints of lines.

Steps of Implementation :

  1. Import the Pycairo module.
  2. Create a SVG surface object and add context to it.
  3. Setting color of the context & line width
  4. Setting of line cap style using set_line_cap( )
  5. Creating a line.

There are three different types line cap styles in PyCairo.

1. set_line_cap ( cairo.LINE_CAP_BUTT )

Example :

Python3




# importing pycairo
import cairo
 
# creating a SVG surface
# here geek94 is file name & 700, 700 is dimension
with cairo.SVGSurface("geek94.svg", 700, 700) as surface:
 
    # creating a cairo context object for SVG surface
    # using Context method
    context = cairo.Context(surface)
    context.set_source_rgba(0, 0, 0, 1)
    context.set_line_width(12)
 
    context.set_line_cap(cairo.LINE_CAP_BUTT)
    context.move_to(30, 50)
    context.line_to(150, 50)
 
    # stroke out the color and width property
    context.stroke()
 
    # printing message when file is saved
    print("File Saved")

Output :

2. set_line_cap ( cairo.LINE_CAP_ROUND )

Example :

Python3




# importing pycairo
import cairo
 
# creating a SVG surface
# here geek94 is file name & 700, 700 is dimension
with cairo.SVGSurface("geek94.svg", 700, 700) as surface:
 
    # creating a cairo context object for SVG surface
    # using Context method
    context = cairo.Context(surface)
    context.set_source_rgba(0, 0, 0, 1)
    context.set_line_width(12)
 
    context.set_line_cap(cairo.LINE_CAP_ROUND)
    context.move_to(30, 50)
    context.line_to(150, 50)
 
    # stroke out the color and width property
    context.stroke()
 
    # printing message when file is saved
    print("File Saved")

Output :

3. set_line_cap ( cairo.LINE_CAP_SQUARE )

Example :

Python




# importing pycairo
import cairo
 
# creating a SVG surface
# here geek94 is file name & 700, 700 is dimension
with cairo.SVGSurface("geek94.svg", 700, 700) as surface:
 
    # creating a cairo context object for SVG surface
    # using Context method
    context = cairo.Context(surface)
    context.set_source_rgba(0, 0, 0, 1)
    context.set_line_width(12)
 
    context.set_line_cap(cairo.LINE_CAP_SQUARE)
    context.move_to(30, 50)
    context.line_to(150, 50)
 
    # stroke out the color and width property
    context.stroke()
 
    # printing message when file is saved
    print("File Saved")

Output:

Note: A line with cairo.LINE_CAP_SQUARE cap used has a different size than a line with cairo.LINE_CAP_BUTT cap. If the line is z units wide, the line with cairo.LINE_CAP_SQUARE cap will be exactly z units greater in size; z/2 units at the beginning and z/2 units at the end.

All three type of line caps can be seen in the below python Example, and the output of each line cap can also be compared 

Python3




# importing pycairo
import cairo
 
# creating a SVG surface
# here geek94 is file name & 700, 700 is dimension
with cairo.SVGSurface("geek94.svg", 700, 700) as surface:
 
    # creating a cairo context object for SVG surface
    # using Context method
    context = cairo.Context(surface)
    context.set_source_rgba(0, 0, 0, 1)
    context.set_line_width(12)
 
    # Setting line cap style
    context.set_line_cap(cairo.LINE_CAP_SQUARE)
    context.move_to(30, 50)
    context.line_to(150, 50)
 
    # stroke out the color and width property
    context.stroke()
 
    # Setting line cap style
    context.set_line_cap(cairo.LINE_CAP_ROUND)
    context.move_to(30, 90)
    context.line_to(150, 90)
    context.stroke()
 
    # Setting line cap style
    context.set_line_cap(cairo.LINE_CAP_SQUARE)
    context.move_to(30, 130)
    context.line_to(150, 130)
    context.stroke()
 
    # printing message when file is saved
    print("File Saved")

Output :


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