Sets A1, A2, and A3 of Color Images

This fileset contains sets A1, A2, and A3 of color images in acquisition devices optical resolutions, that were used in a research described in: R.Starosolski: Reversible denoising and lifting based color component transformation for lossless image compression, submitted. Images are stored in the PPM P6 format (color, binary, 8-bit component depth). A1 is a set of 3 images acquired from a 36mm high quality diapositive film using a Minolta Dimage 5400 film scanner, images stored in device’s optical resolution, image sizes from 7376x4832 to 7424x4864. These images after size reduction and conversion to grayscale where included in the mednat set (http://sun.aei.polsl.pl/~rstaros/mednat/index.html). A2 is a set of 17 images acquired using a general purpose Agfa e50 scanner from 36mm negatives, images stored in device’s optical resolution, image sizes from 1620x1128 to 1740x1164. A3 is a set of 116 images acquired using a Olympus Stylus XZ-2 consumer camera, image sizes 1992x1493. Since the camera detector uses a Bayer-pattern RGGB color filter array, we converted the grayscale Bayer-pattern image to a color image by taking for each group of RGGB subpixels the average of 2 green subpixels as the intensity of green pixel component and intensities of red and blue subpixels as intensities of red and blue pixel components, respectively. This way the image resolution is as close to the detector resolution as possible without interpolation (equal in case of red and blue components, lower for green components). For extracting Bayer-pattern image from RAW camera files dcraw version 9.24 was used (https://www.cybercom.net/~dcoffin/dcraw/).