Ruby Sees the World: Automatic Measurement from Photos March 23, 2026 Published on RubyStackNews What if Ruby could look at a photo of a house and tell you the width of the door, the height of the windows, and the total wall length? That is not science fiction. It is photogrammetry. And it is buildable…

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A walkthrough of building a single-image photogrammetry pipeline in Ruby using ruby-libgd. The approach uses a credit card as a known-size reference object in a photo, then applies edge detection (Sobel via native C), a Hough transform (pure Ruby) to find straight lines, credit card rectangle detection for scale calibration, and finally draws measurement overlays (door width, window height, wall length) on the original image. Full Ruby code is provided for each step, along with performance benchmarks and constraints around the single-plane assumption.