I periodically remind myself that Inkscape can vectorize at least as well as the commercial offerings I looked at. I also remind myself Inkscape's Path->Trace Bitmap... thrives on B&W and lots of bits. I'm working in pure black and white anyway, so that probably helps make trace bitmap appealing. With the slightly new UI, I here make myself another reminder.
Lately, I've been using a ScanSnap to scan in line art. It has a setting to scan at 1200dpi in B&W, producing a bitmap with a color depth of one bit, which is perfect for line art. The product really needs little or no cleaning up if the artwork was clean, so no need to futz with levels and all that since the scanner has done a pretty good job of picking the threshold for black. Unfortunately, it produces that as a PDF, so I have to load it into PhotoShop to either save it to a PNG or copy it to the clipboard for import to Inkscape. I want the 1200dpi due to my rule of thumb that Trace Bitmap... likes lots of bits. Here's a (reduced res) result of scanning some line art with the ScanSnap:
Which seems like a fair job to vectorize. I copy the image to the clipboard from Photoshop, paste it in Inkscape, then run Trace Bitmap. I use Single Scan, Brightness cutoff, and turn off the options (Speckles/Smooth Corners/Optimize). The Brightness Threshold doesn't matter much, since the pixels are pure black and white--0.5 is fine. Press the Update button, then OK, and the result (completed nearly instantly) is fairly indistinguishable from the original bitmap:
Since I didn't ask Trace Bitmap to optimize, this new path has (gulp) over 19,000 nodes. I prefer to do the simplifying outside Trace Bitmap, as someone once showed me. I add the Path->Path Effects "Simplify" effect and play with the controls to trade off reduced nodes versus accuracy. As you can see, it's possible to reduce the node count by a factor of 10 with little loss of accuracy:
The Simplify LPE does not actually get rid of the underlying nodes, which is why you can keep adjusting it all you want. To finalize (and save all that memory), I do Path->Object to Path, to "bake in" the effects of the Simplify LPE. No need to do this, of course, if you aren't concerned about Inkscape starting to get slow or running out of memory.
Sometimes, I have B&W, but not many bits. This xkcd comic has liberal terms for sharing, but not nearly enough bits for printing. I sometimes see xkcd comics reproduced in books and they usually are full of jaggies one expects to see from just simple bitmap enlargement. If I try to vectorize something like that, I typically can't get much better than vectorized jaggies. But, Photoshop can make even an image like that good enough for Inkscape's Trace Bitmap. I took that image, and did a 4x enlargement:
Then I could paste the result into Inkscape and vectorize to get something pretty close to the original, but entirely scalable and capable of print resolutions:
The xkcd source was not pure B&W (has greys), so you have to do some futzing with the Threshold setting in Trace Bitmap to get the results you prefer (I made this one a little darker/thicker-lined than the original). The new UI makes you keep hitting the Update button to do this AFAICT. But still not much work to just fiddle with one setting to get a decent vectorization. IMO, the vectorized result is cleaner and (obviously) less sensitive to any further scale adjustments than just trying to use Photoshop to get the final result.
If you have pure B&W and lots of bits, Trace Bitmap hardly requires any thought to use. But even if you have greyscale and not enough bits, it may be fairly simple to get good results if you have a tool that can do an OK enlargement.
Beyond the Basics In Praise of Trace Bitmap
Inkscape.org
I periodically remind myself that Inkscape can vectorize at least as well as the commercial offerings I looked at. I also remind myself Inkscape's Path->Trace Bitmap... thrives on B&W and lots of bits. I'm working in pure black and white anyway, so that probably helps make trace bitmap appealing. With the slightly new UI, I here make myself another reminder.
Lately, I've been using a ScanSnap to scan in line art. It has a setting to scan at 1200dpi in B&W, producing a bitmap with a color depth of one bit, which is perfect for line art. The product really needs little or no cleaning up if the artwork was clean, so no need to futz with levels and all that since the scanner has done a pretty good job of picking the threshold for black. Unfortunately, it produces that as a PDF, so I have to load it into PhotoShop to either save it to a PNG or copy it to the clipboard for import to Inkscape. I want the 1200dpi due to my rule of thumb that Trace Bitmap... likes lots of bits. Here's a (reduced res) result of scanning some line art with the ScanSnap:
Which seems like a fair job to vectorize. I copy the image to the clipboard from Photoshop, paste it in Inkscape, then run Trace Bitmap. I use Single Scan, Brightness cutoff, and turn off the options (Speckles/Smooth Corners/Optimize). The Brightness Threshold doesn't matter much, since the pixels are pure black and white--0.5 is fine. Press the Update button, then OK, and the result (completed nearly instantly) is fairly indistinguishable from the original bitmap:
Since I didn't ask Trace Bitmap to optimize, this new path has (gulp) over 19,000 nodes. I prefer to do the simplifying outside Trace Bitmap, as someone once showed me. I add the Path->Path Effects "Simplify" effect and play with the controls to trade off reduced nodes versus accuracy. As you can see, it's possible to reduce the node count by a factor of 10 with little loss of accuracy:
The Simplify LPE does not actually get rid of the underlying nodes, which is why you can keep adjusting it all you want. To finalize (and save all that memory), I do Path->Object to Path, to "bake in" the effects of the Simplify LPE. No need to do this, of course, if you aren't concerned about Inkscape starting to get slow or running out of memory.
Sometimes, I have B&W, but not many bits. This xkcd comic has liberal terms for sharing, but not nearly enough bits for printing. I sometimes see xkcd comics reproduced in books and they usually are full of jaggies one expects to see from just simple bitmap enlargement. If I try to vectorize something like that, I typically can't get much better than vectorized jaggies. But, Photoshop can make even an image like that good enough for Inkscape's Trace Bitmap. I took that image, and did a 4x enlargement:
Then I could paste the result into Inkscape and vectorize to get something pretty close to the original, but entirely scalable and capable of print resolutions:
The xkcd source was not pure B&W (has greys), so you have to do some futzing with the Threshold setting in Trace Bitmap to get the results you prefer (I made this one a little darker/thicker-lined than the original). The new UI makes you keep hitting the Update button to do this AFAICT. But still not much work to just fiddle with one setting to get a decent vectorization. IMO, the vectorized result is cleaner and (obviously) less sensitive to any further scale adjustments than just trying to use Photoshop to get the final result.
If you have pure B&W and lots of bits, Trace Bitmap hardly requires any thought to use. But even if you have greyscale and not enough bits, it may be fairly simple to get good results if you have a tool that can do an OK enlargement.