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Behind the pixels

Delve into the world of raster images, channels, color spaces, and pixel data. Learn about entropy in digital images and the differences between formats like JPG and TIFF. Discover the capabilities of the Tagged Image File Format (TIFF) and software tools for image analysis. Explore educational applications and research projects related to image processing.

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Behind the pixels

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  1. Behind the pixels Zsolt Ocskai - DennisGaborCollege 21-04-2015

  2. A few common things about raster images • Their data are stored in pixels • The pixels contain channels • Each channel contains 8 or 16 bits of information • The number of channels is determined by the used colour space: • RGB – RED GREEN BLUE • CMYK – CYAN MAGENTA YELLOW BLACK • Palette – Indexed stored Colours (GIF) • Etc…

  3. A few common things about the raster images R: 90 G: 84 B: 90 Photo by Rita Szabó

  4. Shannonentropy for digital images If we assume pixels are independent from each other, then we fit to use Claude E. Shannon’s entropy formula to process a digital image. possible range of values for the Entropy: Where Where

  5. Shannonentropy for digital images Images properties: JPG 24 bits/pixels RGB HEIGHT 1000 960 WIDTH 643 667 ENTROPY 15,0286 12,453 Photo by Rita Szabó Photo by Péter Vas

  6. Differences between the image formats Images properties: FORMAT JPG TIFF 48 bits/pix. 24 bits/pix. RGB HEIGHT 10000 WIDTH 10000 ENTROPY 24,7204 14,8282

  7. TAGGED IMAGE FILE FORMAT The TIFF is capable of: • Carryingmultipleimages • Storing1, 2, 3, 4, etcchannels/pixel • Storing1, 2, 3, 4, etc… bits/channel • Multipleoptionstoorderthechannels, bytes and bits • StoringLayers For 4 GB physicalstorageboundary

  8. TIFF – amount of channels for 1 pixel RGB RGBA multispectral hyperspectral Capable of carrying more than 359 channels

  9. The 2 main byte - channel orders for 3 pixels in 1 row Interleaved Per Channel I II III I II III I II III I II III

  10. TIFF - head The TIFF is ownedbythe Adobe Inc. and it’sjustpartlyopenedformat. The navigation map forthedatastructurecan be foundintheTAGs. • AllTAGshaveuniqueaddress • SomeTAGsareforbiddentouse / writewithoutAdobe’sapproval Thereareseveralun-official TIFF formats • GEOTIFF • BIGTIFF

  11. The entropy compute software for TIFF images • For the properly TIFF data reading we used the LibTIFF open source libraries • The libraries are available for C++ and .NET environments too and mostly work in the same way We created several applications for more efficient work With the programs we can: - determine the entropy for the whole image - determine the entropy for a single channel Images can be: - 8, 16 bits/channels - 1, 2, 3, 4, etc. Channels/pixel The programs are available for x64 systems: - Windows - Linux - OS X

  12. The software I C++ console and Java GUI For Windows, Linux and OS X enviroments with LibTiff Visual Basic.NET Console and GUI For .NET framework with LibTiff.NET

  13. The software II For JPG, PNG and BMP images C# for .NET 4.0 framework Variants for x86 and x64 systems For educational purpose

  14. Some unusable results Test_8bit_grey.tiff Number of pixels: 2560000 Number of uniquecolours: 256 Entropyvalue : 8 White.tiff Number of pixels: 1000000 Number of uniquecolours: 1 Entropyvalue: 0 Test_24bit_rgb.tiff Number of pixels: 2560000 Number of uniquecolours: 256 Entropyvalue : 8 Black.tiff Number of pixels: 1000000 Number of uniquecolours: 1 Entropyvalue : 0

  15. Where it has been used The researchproject • Educational Applications of Entropy and Fractal Structure Analysis in Impact Assessment of Environmental Pollutions (Journal of Applied Multimedia 2./VIII./2013) • Itwas an agricultural project toanalysethepossibilites of thepollutiondetectionsonimages. • The entropyshowed no significantresults • The SFD (SpectralFractalDimension) wascapable of detectingthedifferentpollutionsintheimages

  16. Important links • „Digitális Fotósuli” - GDF Workshop • SFD Information Technology Ltd. - Digital Image processing web page • Adobe Systems Inc. - Offical TIFF web page • LibTiff project - TIFF handler packages for C++ (remotesensing.org) • LibTiff.NET project - TIFF handler packages for .NET Framework (Bit Miracle) • Research project – researchgate.net

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