PPM or BMP from memory / IO

[jpstroop]

Related to #38 (and following on the solicitation in this comment 😉 ) I have scenario where it would be helpful to do the same with either ppm or bmp images. Would this be feasible?

[jcupitt]

PPM wouldn't be too hard: vips has its own PPM reader, it would just need adapting to take a memory source.

vips8 has vips_magickload_buffer(), it would need wrapping up as a vips7 operation and then adding to ruby-vips.

Even better would be to get the new vips8 Ruby binding working, which has all this stuff already :-( This has hit a series of horrible roadblocks.

[jpstroop]

Thanks for your quick response! I'm afraid I wouldn't know where or how to start if I were to take this on--anything below the Ruby level is probably out of my league. If there is pattern somewhere I could look at, maybe I could take a crack...

[jcupitt]

I've had a quick hack. I'll add patches here as they come in.

It looks like the ppm reader/writer is very wedded to reading and writing files, it would need to be reworked quite a bit to be able to read and write memory as well. I'll have a think.

I've added im_bufmagick2vips() to the vips7 API, it should now be easy to add to ruby-vips.

[jcupitt]

Probably the best solution would be to fix up the load-from-stream branch and merge that, then rewrite the ppm loader to use the stream API.

We should take a look at libgsf as well, perhaps that would be better than load-from-stream.

[jpstroop]

Wow, thanks! Please let me know if there's anything I can do to help.

Speaking of libgsf (though this probably belongs in a separate issue) when trying to install this gem on a fresh Ubuntu 15.04 system, in order to get it to build I had to do:

$ sudo apt-get install libvips-dev
$ sudo apt-get install libgsf-1-dev # i.e. doesn't come in as a dependency of libvips
$ export PKG_CONFIG_PATH=/usr/lib/x86_64-linux-gnu/pkgconfig:$PKG_CONFIG_PATH # pkg-config couldn't find vips
$ gem install ruby-vips

[jcupitt]

It seems to be passing Travis now. You can do stuff like:

irb(main):007:0> png_data = IO.read "k2.png"
irb(main):007:0> require 'vips'
irb(main):007:0> reader = VIPS::MagickReader.new png_data
irb(main):007:0> im = reader.read_buffer
irb(main):007:0> im.x_size
=> 1450

It should handle ppm and bmp images too.

This is loading via libMagick, which is not quick. You may find going via a file and using the vips ppm loader is quicker. It'll certainly use less memory (of course).

I've not pushed this change out as a new version of the gem yet, I'll do a bit more testing (though it now passes the test suite cleanly). You'll also need to build vips from git master, which is annoying.

The new ruby-vips8 binding handles this much better, but needs some work still, sigh.

[jpstroop]

👍 Thanks! I should have time to test over the weekend or early next week.

[jcupitt]

There's a new ruby-vips gem with this feature in. Please open a new issue if there are any problems.

[jpstroop]

Wow, great! I was just thinking that I need to get back to this.