Echo/printf to write images in 5 LoC with zero libraries or headersnetpbm

Been doing this forever. From C it&#x27;s the easiest way to output images, using popen and piping to netpbm or imagemagick. Without error handling it goes like this:<p><pre><code> fp = popen (&quot;pnmtojpeg &gt; output.jpg&quot;, &quot;w&quot;); fprintf (fp, &quot;P3 %d %d 255&quot;, width, height); &#x2F;* print pixels as R G B triples *&#x2F; pclose (fp);</code></pre>

PPM always reminds me of the 2008 winner of the Underhanded C Competition.<p><a href="http:&#x2F;&#x2F;www.underhanded-c.org&#x2F;_page_id_17.html" rel="nofollow">http:&#x2F;&#x2F;www.underhanded-c.org&#x2F;_page_id_17.html</a>

I love love love NetPBM. It’s really easy to drop into your code for debugging or simple image exporting and it is so easy to work with. The amount of information you can get out of a good image is just so high that getting NetPBM output of your complicated thing can be so worth it, even if you are writing it from scratch each time. Plus you can kind of “read” it without an image viewer if you use P1.<p>The other one I really like is Graphviz :)

Very related from 5 days ago:<p><i>How to create minimal music with code in any programming language</i><p><a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=24940624" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=24940624</a><p>Basically pipe values into mplayer, etc.<p>These should go in my #shell-the-good-parts series, which is very backlogged...<p><a href="https:&#x2F;&#x2F;www.oilshell.org&#x2F;blog&#x2F;tags.html?tag=shell-the-good-parts#shell-the-good-parts" rel="nofollow">https:&#x2F;&#x2F;www.oilshell.org&#x2F;blog&#x2F;tags.html?tag=shell-the-good-p...</a>

I&#x27;ve used GIMP as a game level editor this way. Draw your level, save it as PPM, and parse it into tiles in your game. The file is dead easy to parse. For a &quot;real game&quot; you might want to use Tiled or another actual map editor, but for little fun things this is light and Unixy and reliable.

&gt; you can easily slot into Netpbm’s wonderfully Unix-y set of tools by reading&#x2F;writing PPM on stdin&#x2F;stdout<p>No experience with the netpbm suite of tools, but ImageMagick (which TFA mentioned addition to netpbm) supports reading&#x2F;writing any supported format on stdin&#x2F;stdout, the skills of which I dare say are a bit more transferrable. A trivial example:<p><pre><code> $ &lt;my_image.ppm convert ppm:- jpeg:- | convert jpeg:- png:- &gt;my_image.png &amp;&amp; identify my_image.png my_image.png PNG 250x250 250x250+0+0 8-bit sRGB 15836B 0.000u 0:00.000</code></pre>

This reminds me of Wavefront OBJ files, which is the format I use the mostly for a lot of my 3D stuff. It&#x27;s limited but super easy to parse and generate, and macOS Finder can preview it natively.<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Wavefront_.obj_file" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Wavefront_.obj_file</a>

Chris Wellons uses the same format extensively<p><a href="https:&#x2F;&#x2F;nullprogram.com&#x2F;blog&#x2F;2017&#x2F;11&#x2F;03&#x2F;" rel="nofollow">https:&#x2F;&#x2F;nullprogram.com&#x2F;blog&#x2F;2017&#x2F;11&#x2F;03&#x2F;</a> <a href="https:&#x2F;&#x2F;nullprogram.com&#x2F;blog&#x2F;2020&#x2F;06&#x2F;29&#x2F;" rel="nofollow">https:&#x2F;&#x2F;nullprogram.com&#x2F;blog&#x2F;2020&#x2F;06&#x2F;29&#x2F;</a>

When I first heard of these text-based raster image formats, I was surprised at both their inefficiency and seemingly widespread use (outside of PCs), especially given their age.<p>My go-to for uncompressed bitmaps is BMP, also trivial to read and write, and is easy to manipulate the image in memory with indexing operations.

PPM is easy to work with when you&#x27;re close to the metal. I remember one time I bet a MUSH admin that I could get a webcam working on the MUSH command line, and basically implemented an ascii cam over serial using a Parallax Propeller.<p>Won the bet and promptly got kicked from the MUSH. Fun times.

Finding this format might be timely for me. I broke out my TRS-80 CoCo the other day and I&#x27;ve been trying to do some graphics work inside its constraints. Maybe this format, or a variation of it, could work for that.

There is something to be said for simple file formats.<p>I recall making pbms for my Data Structures class in the mid-90&#x27;s. It is definitely a good target for budding programmers.

This is interesting, netpbm is new to me!<p>Is there a similar format for video, which can be generated on the fly without transcoding or invoking ffmpeg?