[Image-SIG] rounded corners

[Stani]

In PIL this is easy.

The following code preferably uses cache (just a simple python
dictionary) to avoid the overhead of generating the same transparency
masks. So typical use would be:

cache = {}
for image in images:
    thumbnail = image_round(image.thumbnail(size, filter), cache, radius)

Here is the code for rounded corners:

# Rounded corners
# (c) 2008 www.stani.be
# License: same as PIL

CROSS                   = _t('Cross')
ROUNDED                 = _t('Rounded')
SQUARE                  = _t('Square')

CORNERS                 = [ROUNDED,SQUARE,CROSS]
CORNER_ID               = 'rounded_corner_r%d_f%d'
CROSS_POS               = (CROSS,CROSS,CROSS,CROSS)
ROUNDED_POS             = (ROUNDED,ROUNDED,ROUNDED,ROUNDED)
ROUNDED_RECTANGLE_ID    = 'rounded_rectangle_r%d_f%d_s%s_p%s'

def round_image(image,cache={},radius=100,fill=255,pos=ROUNDED_POS,
        back_colour='#FFFFFF'):
    if image.mode != 'RGBA':
        image = image.convert('RGBA')
    mask    = create_rounded_rectangle(image.size,cache,radius,fill,pos)
    image.paste(Image.new('RGB',image.size,back_colour),(0,0),
        ImageChops.invert(mask))
    image.putalpha(mask)
    return image

def create_corner(radius=100,fill=255,factor=2):
    corner  = Image.new('L',(factor*radius,factor*radius),0)
    draw    = ImageDraw.Draw(corner)
    draw.pieslice((0,0,2*factor*radius,2*factor*radius),180,270,fill=fill)
    corner  = corner.resize((radius,radius),Image.ANTIALIAS)
    return corner

def create_rounded_rectangle(size=(600,400),cache={},radius=100,fill=255,
        pos=ROUNDED_POS):
    #rounded_rectangle
    im_x, im_y  = size
    rounded_rectangle_id    = ROUNDED_RECTANGLE_ID%(radius,fill,size,pos)
    if cache.has_key(rounded_rectangle_id):
        return cache[rounded_rectangle_id]
    else:
        #cross
        cross_id    = ROUNDED_RECTANGLE_ID%(radius,fill,size,CROSS_POS)
        if cache.has_key(cross_id):
            cross   = cache[cross_id]
        else:
            cross   = cache[cross_id]   = Image.new('L',size,0)
            draw    = ImageDraw.Draw(cross)
            draw.rectangle((radius,0,im_x-radius,im_y),fill=fill)
            draw.rectangle((0,radius,im_x,im_y-radius),fill=fill)
        if pos==CROSS_POS:
            return cross
        #corner
        corner_id   = CORNER_ID%(radius,fill)
        if cache.has_key(corner_id):
            corner  = cache[corner_id]
        else:
            corner  = cache[corner_id] = create_corner(radius,fill)
        #rounded rectangle
        rectangle   = Image.new('L',(radius,radius),255)
        rounded_rectangle   = cross.copy()
        for index, angle in enumerate(pos):
            if angle == CROSS:
                break
            if angle == ROUNDED:
                element = corner
            else:
                element = rectangle
            if index%2:
                x       = im_x-radius
                element = element.transpose(Image.FLIP_LEFT_RIGHT)
            else:
                x       = 0
            if index < 2:
                y       = 0
            else:
                y       = im_y-radius
                element = element.transpose(Image.FLIP_TOP_BOTTOM)
            rounded_rectangle.paste(element,(x,y))
        cache[rounded_rectangle_id] = rounded_rectangle
        return rounded_rectangle


Alex K schreef:
> Hello,
>
> Would anyone know how to generate thumbnails with rounded corners
> using PIL? I'm also considering imagemagick if PIL turns out not to be
> appropriate for the task.
>
> Thank you so much,
>
> Alex
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