testimages - a large-scale archive for testing visual devices and basic image processing algorithms

N. Asuni, A. GiachettiTESTIMAGES: a large-scale archive for testing visual devices and basic image processing algorithmsSTAG: Smart Tools & Apps for Graphics - Cagliari, Italy - September 22-23, 2014 1

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N. Asuni, A. GiachettiTESTIMAGES: a large-scale archive for testing visual devices and basic image processing algorithmsSTAG: Smart Tools & Apps for Graphics - Cagliari, Italy - September 22-23, 2014

TESTIMAGESa large-scale archive for testing visual devices and

basic image processing algorithms

TESTIMAGESa large-scale archive for testing visual devices and

basic image processing algorithms

● Nicola AsuniTecnick.com LTD, UK

● Andrea GiachettiDep. Computer Science, University of Verona, Italy

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Motivation Necessity of digital images to test, evaluate and optimize basic

image processing software and algorithms, physical displays with different resolutions and rendering pipelines.

Necessity of precise geometric and color patterns at different resolutions.

Difficulty to find the exact images used by others and be able to reproduce and compare results.

Ability to save time by reusing a ready-made dataset. Limitations imposed by different image licensing and copyright

laws in different countries. Lack of a large common or standard dataset of hi-quality test

images for basic image processing.

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INTRODUCTION TESTIMAGES EXAMPLES DISCUSSION

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Another Image Dataset? Good image datasets are available but they are not

generally suitable for research due to their unknown source, poor quality or licensing/copyright issues.

Numerous research-oriented image archives (e.g. computervisiononline.com) are only useful or specific tasks (e.g. PASCAL dataset for semantic annotation, LIVE for image quality assessment, others for faces, textures, etc.)

There are not large datasets for patterns and colors at multiple standard display resolution and quality assessment for image rescaling.

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Proposed Solution Publicly available, large and free collection of digital images

(TESTIMAGES) mainly designed for analysis and quality assessment of different kinds of displays (i.e. mobile phone screens, monitors, televisions and digital cinema projectors) and basic image processing tecnhiques (i.e. resampling, rendering, perception).

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Main Features Publicly available : http://testimages.tecnick.com Free licence : CC BY-NC-SA 4.0

Creative Common licence Attibution-NonCommercial-ShareAlike 4.0 International

High resolution 16bpp and 8bpp, RGB and Grayscale images. Multiple datasets with hundreds of different artificial (computer-

generated) and natural reference images. More than 2 million ready-made images, counting the

variations in color, bit-depth and resolution. Availability of shifted downscaled images for resampling and

superresolution algorithms. Common file naming convention.

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http://testimages.tecnick.com/

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Archive Organization The archive is currently organized in four main sections:

● COLORmainly aimed at testing color rendering on different displays

● PATTERNSmainly aimed at testing the rendering of standard geometrical patterns

● SAMPLING and SAMPLING_PATTERNSmainly aimed at testing resampling algorithms

Despite their main categorization, the images can be easily repurposed for different scenarios.

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COLOR Computer-generated Images mainly aimed to test the

color rendering on different displays and facilitate color adjustments and calibration.

7 reference RGB images, including the standard SMPTE RP 219:2002 calibration image, all available in 16bpp and 8bpp for 114 different standard and common resolutions up to 16K Digital Cinema (16384x8640).

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PATTERNS Computer-generated images mainly aimed to test the

rendering of standard geometrical patterns by display, monitors, televisions and projectors, facilitating the calibration process and the detection of defects.

38 base patterns with multiple variations, available in Grayscale and RGB with different color channel combinations, 16bpp and 8bpp and adapted for 114 standard and common resolutions.

Helps to optimize or identify specific issues in some image processing algorithms.

Some patterns can be used as graphic masks.

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SAMPLING Natural images mainly aimed at testing resampling

algorithms (i.e. interpolation, zooming, enlargment and superresolution).

40 RBG 1224x1224 pixels 16bpp HDR reference images.

Subresolution and variations with 8bpp and grayscale, for a total of more 220K images.

An approach involving multiple camera exposures was used to acquire 16bpp HDR natural images since there are not 16bpp capable photographic cameras in the consumer market.

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SAMPLING PATTERNS Aim to test in isolation specific features of resampling

algorithms. This is an extension of the SAMPLING archive

containing 424 artificial Grayscale reference images, generated as described in the PATTERNS section for the 1224x1224 pixels resolution, for a total of more than 1 million image variations.

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Evaluation of upscaling algorithms The SAMPLING and SAMPLING_PATTERNS datasets

can be used to evaluate upscaling algorithms with enlarging factors of 2, 3, 4, 5, 6, 8, 10 and 12.

Subsampled and shifted images are available to account for the half-pixel shifts introduced by hole-filling interpolation methods.

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original pixels

sub-sampled pixels (C00C00)

shifted interpolated pixels using hole-filling method(B01R01)

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Display Calibration In the COLOR dataset, the resized variations of the

standard SMPTE RP 219:2002 image can now be used to calibrate different resolutions. The other images can be used to calibrate features like color balance, gamma and saturation.

The images in the PATTERNS dataset can be used to calibrate features like contrast, clock, phase, sharpness and gradient banding.

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Discussion Research and development in Computer Graphics and

image processing may obtain huge benefit from the availability of public tools for the technical and scientific community.

The TESTIMAGES archive is proposed as a ready and free to use large image dataset with different image types for different purposes.

The archive has been already downloaded thousands of times and used in scientific publications.

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http://testimages.tecnick.com

testimages - a large-scale archive for testing visual devices and basic image processing algorithms

Science

calibration image

largescale archive

different image licensing

smart tools apps

graphics cagliari

good image datasets

testing color rendering

testing resampling algorithms