Thumbnailer

Thumbnail images using akka-streams

PNG

Command Line

Usage: --in <input file> [--out <output file>] [--scalewidth <width scaling>] [--scaleheight <height scaling>]

This will scale the input file by the given ratios using an averaging method.

Web App

When running go to http://localhost:8080

Fill in the form and hit submit, the resized image should appear to the side.

Library

• Flows to parse a PNG into a stream of chunks and vice-versa
• Flows to decompress/compress the pixel data stream
• Stage to unfilter the pixel data stream
• Stage to filter the pixel data stream using a heuristic to choose an optimal filter for each line.
• Stages to transform unfiltered pixel data by
• Downsampling (picking a subset of pixels)
• Averaging (averaging pixels)

Known Issues

• Does not support interlacing
• The deflate/inflate stages (taken from akka-http) seem to get upset at some images - reasons unclear
  • Reducing the size of the chunks entering the deflater seems to help (indicating there's a bug in the deflater)
  • Some images fail even with very small chunks
  • Seems to happen more with large images, but that may just be because there's more to go wrong
• Likely to be horribly inefficient. It uses a ByteBuffer for particularly intensive operations, but the streams have significant overhead.
• The web app behaves quite poorly on failure - as it's all streamed if there's a failure it just times out.