Embedded alpha channels (masks) aren't removed from file when the images are deleted

[Guillermo Espertino (Gez)]

I just found that alpha channel from embedded images isn't removed from the SVG file when the embedded images are deleted.
I created a copy of an existing file with embedded images, deleted those images and saved, and the result was the attached file, 1.2 MB for a file with two short text blocks and cropping marks.
I wondered why the file was so heavy, and fond that the alphas were still embedded.

[su_v (suv-lp)]

Did you embed those images with Inkscape or was the file initially imported as PDF? (reminds me of the masked images in the SVG files attached to bug #427540)
Did you try to unmask/unclip the images before or use 'vacuum defs' after deleting them?

[Guillermo Espertino (Gez) (gespertino-gmail)]

Hmm. Good tip. I have to do further investigation about this.
Now you mention it, maybe it was an imported PDF. I can't remember, but I'll try and report my findings.

Thanks for the feedback.

[Guillermo Espertino (Gez) (gespertino-gmail)]

~suv: The vacuum defs command worked fine. I guess I have to use it more frequently. :-)
The file was indeed an imported PDF from Illustrator, so this report starts to look invalid.
I'd just like to know if this kind of stuff is covered in the documentation. Never read something about it (maybe I simply missed it).

[Pablo Trabajos (pajarico)]

> Did you try to unmask/unclip the images before or use 'vacuum defs' after deleting them?
But shouldn't deleting the images remove any def relative to the them?

[su_v (suv-lp)]

I can reproduce it with the example in bug #427540 <http://launchpadlibrarian.net/31617709/%5C192.168.10.12%5Cgordon%5Cwork%5C2007-ft2%5Cpower-distribution%5Celectrodes-and-clamps-channel-and-forehearth%5C090909-troubleshooting-inkscape-and-pdfs%5Cone-saved-after-opening-original-pdf.svg> :

enter the groups with double-click until you can select an illustration (rather: it's a grouped rectangle with a mask containing the image in the defs section) and delete the object (rectangle) that looks like the image itself.

Result: the image is gone (on canvas) but the embedded bitmap stays in the defs mask definition.
expected: original embedded image in the mask gets removed as well.

Mask:
<mask
       maskUnits="userSpaceOnUse"
       x="0"
       y="0"
       width="1"
       height="1"
       id="mask159"><image
         width="1"
         height="1"
         xlink:href="data:image/png;base64, (…snipped…)"
         id="image161" /></mask>

Illustration:
<g
             id="g157"
             transform="matrix(188.872,0,0,117.055,300.167,240.278)"><rect
               x="0"
               y="0"
               width="1"
               height="1"
               transform="matrix(1,0,0,-1,0,1)"
               style="fill:#000000;fill-opacity:1;fill-rule:nonzero"
               mask="url(#mask159)"
               id="rect163" /></g>

[su_v (suv-lp)]

workaround: select the (masked) rectangle, release the mask and delete both the image (now in place and no longer in the defs section) and the rectangle.

But why would you use this kind of inverse masking to get a B&W raster image embedded?

[su_v (suv-lp)]

all wrong: Inkscape leaves any clipping and masking defs behind when deleting masked or clipped objects.

attached file has for 4 variations of clip and mask:
text (as path) masks rectangle
rectangle masks text
text (as path) clips rect
rect clips text

remove the visible text objects with 'delete', check the <defs> section: all clip and mask definitions are still present.
(with Inkscape 0.46+devel r22401, OS X)

[su_v (suv-lp)]

…looks like an empty file after deleting the four text objects but the <defs> stay behind. Intentional?