Method A
From the cairo samples, modified. Gives a very nice shape but takes width and height only as guides.
def roundedrecA(self,cr,x,y,width,height,radius=5):
#/* a custom shape, that could be wrapped in a function */
#radius = 5 #/*< and an approximate curvature radius */
x0 = x+radius/2.0 #/*< parameters like cairo_rectangle */
y0 = y+radius/2.0
rect_width = width - radius
rect_height = height - radius
cr.save()
#cr.set_line_width (0.04)
#self.snippet_normalize (cr, width, height)
x1=x0+rect_width
y1=y0+rect_height
#if (!rect_width || !rect_height)
# return
if rect_width/2<radius:
if rect_height/2<radius:
cr.move_to (x0, (y0 + y1)/2)
cr.curve_to (x0 ,y0, x0, y0, (x0 + x1)/2, y0)
cr.curve_to (x1, y0, x1, y0, x1, (y0 + y1)/2)
cr.curve_to (x1, y1, x1, y1, (x1 + x0)/2, y1)
cr.curve_to (x0, y1, x0, y1, x0, (y0 + y1)/2)
else:
cr.move_to (x0, y0 + radius)
cr.curve_to (x0 ,y0, x0, y0, (x0 + x1)/2, y0)
cr.curve_to (x1, y0, x1, y0, x1, y0 + radius)
cr.line_to (x1 , y1 - radius)
cr.curve_to (x1, y1, x1, y1, (x1 + x0)/2, y1)
cr.curve_to (x0, y1, x0, y1, x0, y1- radius)
else:
if rect_height/2<radius:
cr.move_to (x0, (y0 + y1)/2)
cr.curve_to (x0 , y0, x0 , y0, x0 + radius, y0)
cr.line_to (x1 - radius, y0)
cr.curve_to (x1, y0, x1, y0, x1, (y0 + y1)/2)
cr.curve_to (x1, y1, x1, y1, x1 - radius, y1)
cr.line_to (x0 + radius, y1)
cr.curve_to (x0, y1, x0, y1, x0, (y0 + y1)/2)
else:
cr.move_to (x0, y0 + radius)
cr.curve_to (x0 , y0, x0 , y0, x0 + radius, y0)
cr.line_to (x1 - radius, y0)
cr.curve_to (x1, y0, x1, y0, x1, y0 + radius)
cr.line_to (x1 , y1 - radius)
cr.curve_to (x1, y1, x1, y1, x1 - radius, y1)
cr.line_to (x0 + radius, y1)
cr.curve_to (x0, y1, x0, y1, x0, y1- radius)
cr.close_path ()
cr.restore()
Method B
From mono moonlight aka mono silverlight. Works very well on larger shapes.
def roundedrecMoonlight(self,cr,x,y,w,h,radius_x=5,radius_y=5):
#from mono moonlight aka mono silverlight
#test limits (without using multiplications)
# http://graphics.stanford.edu/courses/cs248-98-fall/Final/q1.html
ARC_TO_BEZIER = 0.55228475
if radius_x > w - radius_x:
radius_x = w / 2
if radius_y > h - radius_y:
radius_y = h / 2
#approximate (quite close) the arc using a bezier curve
c1 = ARC_TO_BEZIER * radius_x
c2 = ARC_TO_BEZIER * radius_y
cr.new_path();
cr.move_to ( x + radius_x, y)
cr.rel_line_to ( w - 2 * radius_x, 0.0)
cr.rel_curve_to ( c1, 0.0, radius_x, c2, radius_x, radius_y)
cr.rel_line_to ( 0, h - 2 * radius_y)
cr.rel_curve_to ( 0.0, c2, c1 - radius_x, radius_y, -radius_x, radius_y)
cr.rel_line_to ( -w + 2 * radius_x, 0)
cr.rel_curve_to ( -c1, 0, -radius_x, -c2, -radius_x, -radius_y)
cr.rel_line_to (0, -h + 2 * radius_y)
cr.rel_curve_to (0.0, -c2, radius_x - c1, -radius_y, radius_x, -radius_y)
cr.close_path ()
Method C
I can't remember where I got this. If you are the author please add your name. Works well on smaller shapes.
def roundedrec(self,context,x,y,w,h,r = 10):
"Draw a rounded rectangle"
# A****BQ
# H C
# * *
# G D
# F****E
context.move_to(x+r,y) # Move to A
context.line_to(x+w-r,y) # Straight line to B
context.curve_to(x+w,y,x+w,y,x+w,y+r) # Curve to C, Control points are both at Q
context.line_to(x+w,y+h-r) # Move to D
context.curve_to(x+w,y+h,x+w,y+h,x+w-r,y+h) # Curve to E
context.line_to(x+r,y+h) # Line to F
context.curve_to(x,y+h,x,y+h,x,y+h-r) # Curve to G
context.line_to(x,y+r) # Line to H
context.curve_to(x,y,x,y,x+r,y) # Curve to A
return