1. Image formats Characteristics © Adolf Knoll, National Library of the Czech Republic

2. What a format does contain? Information about:  Resolution (vertical and horizontal)  Colour depth  Compression  … a lot of other data to enable the correct display or printing (ICC profiles, e.g.) Some formats offer only selected opportunities.

3. Types of image formats ISO initiatives (TIFF; JPEG, JBIG, /MPEG/) De facto standards (PNG) Very proprietary formats (PSP, PSD, ZMF, … - internal formats of graphical tools)

4. TIFF – Tagged Image File Format ISO definition A container that can incorporate so many parameters This may cause various problems with reading or writing TIFF

5. TIFF and write/read problems Black and White (1bit, 2 colours)  Huffman RLE encoding  CCITT Fax Group 3  CCITT Fax Group 4 (TIFF 4) Colour (up to 24 bits, true colour)  no compression  LZW (TIFF 5)  Mackintosh Packbits  JPEG (TIFF 6)  PNG

6. True Colour Black and White

7. Grey scale 256 shades of grey Grey scale 16 shades of grey Black and White 2 colours 8 bit4 bit 1 bit

8. 24 bit/True colour 8 bit 4 bit 16,7 million colours 256 colours16 colours

9. TIFF Fax Group 4 TIFF can also contain more images (multipage TIFF, gr. 6) in one.multipage TIFF

10. BMP Microsoft Windows Bitmap It supports 16,7 million colours, frequently only with 256 colours It supports RLE compression Fast reading as any other uncompressed bitmap

11. Web image formats There are 3 formats recommended by the WWW consortium for web: GIF JPEG PNG (latest recommendation) … and also SVG

12. GIF Graphic Interchange Format 256 colours - palette format each GIF has its own palette this is difficult to combine LZW compression scheme highly used on the web several modifications in the WWW environment used frequently as the so-called transparent, interlaced, or animated GIF

13. Palettes of GIF images

14. Transparent GIF One colour in the 256-colour palette can be indicated as transparent

15. Animated and Interlaced GIF Animated GIF on web pages Animated GIF Interlaced GIF as many other formats can appear successively step by step

16. JPEG Joint Photographic Expert Group True colour, 24 bit Lossless or lossy compression: the compression ratio must be tuned individually (software dependent) Possibly progressive encoding (not recommended - read problems possible) irreplaceable for compression of photorealistic images

17. PNG Portable Networks Graphic True colour format; allows up to 48 bit encoding PNG compression: lossless, 9 degrees Slightly more economic compression than GIF, but more colours transparency (alpha-channel) possible, interlaced character possible

18. WWW and images 3 formats are recommended by the WWW consortium: GIF, JPEG, PNG (recently) Other formats possible, but they require special components to be installed into web browsers (ActiveX, plug-ins).