A Libre Graphics Meeting showcase summary

Every year, there are a variety of talks at Libre Graphics Meeting that showcase entirely new work. While these new-project sessions frequently highlight still-in-development ideas or code that may not be quite ready for packaging and mass distribution, they are always a fascinating counterpoint to the progress reports from established application projects. At this year's event, the new projects showed off work designed to help crowdsource image collection, to do desktop publishing with HTML, and to transform 3D meshes into 2D images and back again.

The List

Matt Lee, technical lead at Creative Commons, introduced The List in a session on the first day of the event. The List is, in essence, a social-networking system in which users post public requests for images, and other users respond by posting matching images—images they have created from scratch, photographs they have taken, physical artwork they have scanned, and so forth. The project uses a free-software Android app as its interface, with an iOS app to follow shortly.

The crux of the problem that The List sets out to solve is that everyone needs images to communicate, but few people have the skills to create high-quality imagery (even among people for whom open content is a priority). The main example Lee discussed was contributions to Wikipedia; his talk was (not coincidentally) scheduled right after one from a Wikipedia volunteer who described that project's efforts to generate higher-quality SVG illustrations.

The app was developed with support from the Knight Foundation, and ultimately aims to be useful for a range of purposes, including collecting images for journalists, non-profits, and cultural institutions. The goal is a lofty one; harnessing the collective power of crowds to find obscure or out-of-print cultural works, for example, is arguably a higher calling than filling in missing photographs of buildings on Wikipedia. Creative Commons also plans to use The List app as a means to explain the values behind Creative Commons itself: at first startup, users are given a walkthrough of Creative Commons licenses before they are presented with the categorized list of requested images.

At the end of the talk, Lee outlined several of the challenges facing the project team. Internationalizing the requests for images is a hard problem, he said, relying as it does on human language and cultural context. There is also concern about whether or not the average smartphone camera will produce photos good enough to meet the needs of the people making image requests. The List's backend is not limited to smartphone photos, of course (all of the uploaded images are stored at The Internet Archive, which can handle essentially any file type). A web or application-based interface could easily allow the upload of other image types. The future of The List may include support for these other upload types—among other features, like enabling the device's geographic location to alert the user to nearby image-taking opportunities.

Finally, there is the question of image and request moderation. Balancing the desire for an open community with the Internet's tendencies for attracting trolls is a difficult challenge, to be sure. But it is one that Creative Commons, Wikipedia, and the Internet Archive have all worked at maintaining for several years now.

html2print

On the second day of the conference, Stéphanie Vilayphiou of Open Source Publishing (OSP) presented a talk about html2print, its tool for doing print-ready page layout using HTML and CSS. Printable web documents are not a new idea, of course, but many of the contemporary projects rely heavily on the HTML5 <canvas> element. That makes the resulting output more like a drawing than a text document: individual elements are not accessible through the document object model (DOM), and there is no separation between the code and the design.

Html2print relies on some lightweight CSS tools (such as the preprocessor LessCSS). It defines page dimensions (including paper size and margins) as CSS properties, so that they can be adjusted and inspected easily, and allows the creation of re-flowable text elements using CSS Regions. It even allows the user to define CMYK spot colors as separate "inks" that can then be "mixed" in individual elements (e.g., 40% of chartreuse_1 and 15% eggshell_2). That feature is particularly useful for print work, because by default HTML and CSS only support RGB color at 8-bit-per-color granularity.

OSP likes to use collaborative editors like Etherpad for all of its projects, and html2print is designed to support that. It lets multiple users edit a large project simultaneously. It also supports what she called "responsive print" (a reference to responsive web design). She showed a demonstration using a booklet project: resizing the page-size parameters automatically adjusts other properties (like font size) to match. Large-format, book-like dimensions trigger a lot of text per page, while scaling the page dimensions down to pocket size proportionally scales the text so that its printed size will remain readable.

Vilayphiou explained a few of the challenges that OSP had to tackle along the way, such as implementing a new zoom tool. Relying on the web browser's zoom function was a bad idea, she said, because zooming invariably triggers a re-render operation, which often causes difficult-to-fix artifacts. The zoom tool was more or less a solved problem, she said, but others have proven trickier—such as the inherent instability of the various browser engines. Two years ago, for instance, Chrome worked perfectly, but then the project dropped WebKit for its own Blink engine and discontinued support for CSS Regions.

Vilayphiou closed out the session by noting that html2print does not yet have a proper license attached, which she said was simply an accident. She encouraged anyone with interest in preparing print documents for publication to take a look and offer feedback, although at this stage new users might need to set time aside to learn their way around the tool.

Embedding 3D data in 2D images

Architect Phil Langley presented what he called a "digital steganography" project in his session on day three. Steganography is often associated with hiding information, he said, but the term originally just referred to embedding one message inside another. The most common example is encoding a string inside the least-significant bits of an RGB image, but Langley showed several other real-world techniques, such as an audio track embedded in a photograph, and concealing one text message within another. He also noted that depth-map images such as those produced by the Microsoft Kinect camera are actually encoding 3D data in a 2D form.

That final example leads into the project that Langley undertook. A course he teaches at the Sheffield School of Architecture involves advanced 3D modeling, and he recently set up a Twitter bot to send out status reports as the software progressed through its calculations. The trouble was that tweets are only 140 characters long, which is hardly enough to explain progress in detail. So the team set out to hack a solution that used a different feature instead. Twitter allows large images to be attached to Tweets, so the team looked for a way to encode their 3D meshes as 2D images.

The initial attempt was fairly straightforward. Each face of a typical 3D model is a triangle, and each vertex of that triangle includes three coordinates (x,y,z). They tried mapping the (x,y,z) triples to RGB values, thus using three pixels to represent each triangle. While this worked, it did not provide much resolution: 8-bit-per-channel graphics allowed just 256 units in each spatial dimension, which is quite coarse.

After further refinement, they settled on a plan that used the 24 bits of an RGB pixel to encode vertex coordinates more efficiently. The 3D model is first sliced into thin horizontal bands; each band has far fewer units in the z direction, so more resolution is available for the x and y coordinates. Furthermore, the resulting image somewhat resembles a 2D projection of the model.

This encoding scheme allowed the class's Twitter bot to generate and send PNG images that could quickly be converted into 3D models. The compression ratio was impressive, too: Langley showed a 6.7KB PNG image that represented a 156.8KB file in the STereoLithography (STL) format.

But that was not the end of the experimentation. Once the image-based format was working, Langley and the students started experimenting with altering the PNGs in GIMP and other image-editing tools. Some image transformations would have a predictable effect on the resulting 3D model (such as stretching or compressing), while others were more chaotic. There were practical uses to treating the models as 2D images, too—Langley showed a tool that graphed the changes in a model over time by plotting each step's 2D image together in a sequence.

These three sessions might not be described as a representative sample of LGM 2015, consisting, as they do, of such wildly different projects. But they do provide a glimpse into what makes the conference interesting every year. Html2print has clear application for those in the publication-design field, while Langley's 3D-to-2D object transformation is notably more experimental, and The List presents an interesting new take on consumer-grade content creation. Together, they are nothing if not thought-provoking.