Draw does not work on a SingleImage

[rkpatel33]

I have a multi-page PDF on which I want to draw some annotation, however, when I try to call draw.draw(singleimage) Wand throws an error:

TypeError: image must be a wand.image.Image instance, not <wand.sequence.SingleImage: 947cceb (612x792)>

Here is my sample code:

image = Image(filename='Acme.pdf')
singleimage = image.sequence[0]

draw = Drawing()
draw.stroke_color = Color('transparent')
draw.stroke_width = 1
draw.fill_opacity = 0.10
draw.fill_color = Color('rgba(0, 0, 255, 0.10)')
draw.rectangle(left=0, top=0, right=200, bottom=792)

draw.draw(singleimage)

Is this a bug or is there a reason this not possible? If you simply call the same code on the whole document image instead with draw.draw(image), it draws the rectangle on the last page, which is also odd behavior.

PDF is attached.

Acme.pdf

[emcconville]

Why not? The current wand.drawing.Drawing.draw method validates for an instances of wand.image.Image, but there's no reason to validated for wand.image.BaseImage instead. (but I might be wrong)

Workaround

Create a new instance of wand.image.Image from sequence slice.

from wand.image import Image
from wand.color import Color
from wand.drawing import Drawing

with Image(filename='Acme.pdf') as image:
    with Image(image.sequence[0]) as singleimage:
        with Drawing() as draw:
            draw.stroke_color = Color('transparent')
            draw.stroke_width = 1
            draw.fill_opacity = 0.10
            draw.fill_color = Color('rgba(0, 0, 255, 0.10)')
            draw.rectangle(left=0, top=0, right=200, bottom=792)
            draw.draw(singleimage)

Another workaround

Extend wand.drawing.Drawing.draw to validate against BaseImage. Untested

from wand.drawing import Drawing
from wand.image import BaseImage

class MyDrawing(Drawing):
    def draw(self, image):
        if not isinstance(image, BaseImage):
            raise TypeError('image must be a wand.image.BaseImage instance, not '
                            + repr(image))
        res = library.MagickDrawImage(image.wand, self.resource)
        if not res:
            self.raise_exception()