# Last edited on 2023-01-22 03:20:40 by stolfi

GOAL

  This project is a collection of square images of standard sizes
  with miscellaneous shapes and textures for image processing experiments,
  such as texture generation from examples.
  
FINAL IMAGES

  The final texture images are stored in 8-bit PNM format, with linear encoding (gamma=1),
  in the following self-explanatory directories:
  
    ppm-400x400/*.ppm (color)

    pgm-512x512/*.pgm (grayscale)
    pgm-256x256/*.pgm (grayscale)
    pgm-128x128/*.pgm (grayscale)

  The image names have all the form "{AAAAA}-{NN}.ppm" or "{AAAAA}-{NN}.pgm"
  where {AAAAA} is a lowecase alpha name that sort of describes the image
  contents, like "trees" or "pabbl"; and and {NN} is a 2-digit number to 
  distigush images with same {AAAAA}.
    
  The directories "pgm-256x256" and "pgm-128x128" have scaled versions
  of the images in "ppm-400x400", converted to grayscale and slightly
  contrast-stretched. 
  
  The irectories "pgm-256x256" and "pgm-128x128" also have scaled-down
  versions of any image "pgm-512x512/{AAAAA}-{NN}.pgm" when the color
  version "ppm-400x400/{AAAAA}-{NN}.ppm" does not exist.

  The images "wavys-{NN}.pgm" and "wavys-{NN}.ppm" are exceptions
  to the above.  They are NOT scaled versions of each other, but are 
  created directly with the specific size. See below.

ORIGINAL IMAGES

  Some of the original images that have already been converted to "ppm-400x400" 
  and/or "pgm-512x512" are in "orig/processed/raw/". Those still to be processed
  to the end are in "orig/to-process/raw/".
  
  These images have arbitrary names and sizes, and may be in various formats 
  like ".png", ".jpg", ".tiff", ".gif", etc.
  
HAND-PROCESSING OF ORIGINAL COLOR IMAGES

  Generally, the original versions of the "ppm-400x400" textures are
  pre-processed by hand (using e.g. gimp). The pre-processing
  typically includes scaling, contrast-stretching, and cropping to a
  square format, at least 400x400 pixels.

  The result of the hand-processing is generally saved in the 
  "orig/processed/cropped-square/", already with the final 
  name "{AAAAA}-{NN}.{ext}".  The format {ext} is usually "png",
  but other formats have been used for older images.

FINAL SCALING AND CONVERSION OF COLOR TEXTURES

  The script {process_raw_files.sh} has been used to convert each image "{AAAAA}-{NN}.{ext}"
  in "orig/processed/cropped-square" to the final file "ppm-400x400/{AAAAA}-{NN}.ppm"
  The processing includes contrast-stretching, reencoding with linear gamma, and quantization
  to 8 bits per channel.

GRAYSCALE IMAGES
  
  The images in pgm-512x512 were created by hand directly from the original images,
  mostly lost by now.

  Every image "ppm-400x400/{AAAAA}-{NN}.ppm" (except the "wavys" images, see below)
  is converted to grayscale and further scaled down
  to produce "pgm-256x256/{AAAAA}-{NN}.pgm" and "pgm-128x128/{AAAAA}-{NN}.pgm". This is 
  done by the script {gen_grays_from_ppm_400x400.sh}.
  
  Also, every image "pgm-512x512/{AAAAA}-{NN}.pgm" that does not have a
  color version "ppm-400x400/{AAAAA}-{NN}.ppm" (except the "wavys"
  images, see below) is scaled down to produce
  "pgm-256x256/{AAAAA}-{NN}.pgm" and "pgm-128x128/{AAAAA}-{NN}.pgm".
  This is done by the script {gen_grays_from_pgm_512x512.sh}.

WAVYS IMAGES

  The images "wavys-{NN}.ppm" and "wavys-{NN}.pgm", of any size,
  are generated directly by {libimg/tests/335_waves/waves_test.c},
  with no scaling or color modifications.