Warning: Inkscape & Bitmaps do not mix


#1

A friend sent the attached logo for her restaurant to play with. Easy enough. Drag the PNG into the GFUI, then add a circle to cut it out.

Works great! But then I wanted to combine the cut with the bitmap so I could replicate the pattern in the GFUI easily at different sizes.

Dropping the image into InkScape and adding a circle was straightforward. However, the SVG imported from InkScape into the GFUI totally mucked up the bitmap. Lots of aliases and weird blocky effects.

Doing the same in Boxy SVG (A random SVG editor on OS X from the App Store-- it isn’t that great, but it isn’t awful either) works fine.

So, bottom line, be aware that InkScape + Bitmaps can end poorly.


#2

Can you post a screenshot of when it went wrong so we know what to look out for? (The pictures you posted looked pretty good)


#3

Sorry-- meant to add this to the original.

The first image is the result of Inkscape’s mucking up the image. The second is via Boxy. I also tried saving as PDF from Inkscape, but that didn’t work at all due to the PDF having an embedded JPG and no a PNG with transparent background.

55 AM07 AM


#4

And these are the two SVG files; one from Inkscape and one from Boxy SVG.

(Wow. It appears that the forum really can’t deal with SVG files at all well. Adding a ZIP.)

Hungry Minnow GoodBad.zip (656.0 KB)

Hungry Minnow (Inkscape)Hungry Minnow (Boxy)


#5

On the Mac, there is another issue that can also mess you up with inkscape: unless you get your XQuartz settings just right (XQuartz is the graphics layer that translates between the linuxy inkscape code and the Mac UI), cut-and-paste of pretty much anything gets messed up. You need to turn off synching between the X clipboard and the Mac clipboard iirc.

Don’t know if that contributed to this particular problem, but it’s something for people using
the mac version of inkscape to watch out for


#6

Great tip. I already have the setting set and it didn’t contribute to this issue. No copy/paste involved.

This is the setting in Xquartz, btw. It mostly impacts the copy/paste of vectors. Specifically, if you want to disable this setting.

03 AM


#7

I haven’t seen this issue myself so haven’t tested it. This issue has been seen when a bitmap is rotated or scaled. Even though the image looks horrible in the UI it may engrave just fine. Try it out on a scrap of cardboard if you want to test it and not ruin some good material.

I suspect that the file has a rather large preview image that is getting drastically reduced when manipulated. The GUI is using the preview and the processing is using the image.


#8

There are known problems such as rotating bitmaps inside some vector drawing programs including Inkscape and remember to never save a file as InkscapeSVG. Only Plain SVG.

Have had the blocky appearance in both the GUI and in the print when I rotated the bitmap.

Haven’t had it happen with Inkscape otherwise.


#9

Thirding that XQuartz configuration note about Pasteboard/CLIPBOARD. Having that toggle wrong is ruinous for any cut and paste work in Inkscape on my OSX setup; I got it toggled correctly the first time I installed it on my iMac a year and change ago, and then didn’t get it right when installing on my macbook a few weeks ago and was deeply frustrated for a couple days before I went googling and turned that up.

In general Inkscape has been fine about bitmap/raster images for me, though I’ve done not very much engraving work so far with the GF so I haven’t stress-tested it yet.


#10

Yeah-- I didn’t have it toggled correctly for a long while, apparently. Just discovered this because – SURPRISE! – some of the SVG files from my old Christmas tree ornament printer (see EggBot from EMSL) had some “vectors” that were actually rasterized images.


#11

I think it’s something on the rendering side. PNG files are lossless but the program that’s re-displaying the PNG is the one that needs to decode the compression. So it appears that the GFUI is not decoding the compression and thus not rendering the image true to form. It could be something to do with PNG’s being stuck inside SVG files.

Case in point…

What the GF app displays: (This was NOT a rotated bitmap)

The actual engrave results:


#12

OK-- so, it looks like it is potentially a cosmetic issue only.

That’s good to know.

And I’m happy to have a workaround via a second app (Boxy SVG).


#13