Multimedia Systems Part 5

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Multimedia Systems Part 5 Mahdi Vasighi www.iasbs.ac.ir/~vasighi Department of Computer Science and Information Technology, Institute for Advanced Studies in Basic Sciences, Zanjan, Iran Image Formats PNG o Portable Network Graphics o Developed in early 1995 as an alternative to GIF o Three advantages over GIF • Alpha channel (up to 16 bits) • Gamma correction • 2D Interlacing Image Formats - PNG Interlacing o Adam7 algorithm • operates in both dimensions • uses seven passes and through each 8 × 8 block of an image Image Formats - PNG Interlacing Pass 1 Pass 2 Pass 3 Pass 4 1/64 = 1.5625% 1/32 = 3.125% 1/16 = 6.25% 1/8 = 12.5% Pass 5 Pass 6 Pass 7, 1/4 = 25% 1/2 = 50% 1/1 = 100% Image Formats - PNG Interlacing ADAM7 Pass 4 Row-wised Pass 1 1/8 = 12.5% 1/8 = 12.5% PNG GIF GIF pixels have an 8-to-1 aspect ratio, whereas PNG pixels are 2-to-1 Image Formats - PNG Interlacing ADAM7 Pass 5 Row-wised Pass 2 1/4 = 25% 1/4 = 25% PNG GIF GIF pixels have an 4-to-1 aspect ratio, whereas PNG pixels are 1-to-1 Image Formats - PNG PNG GIF interlacing interlacing Image Formats - PNG PNG • Supports up to 16 bits per pixel in each color channel • Supports lossless compression • Does not support multiple image format/ animation like GIF • embedded textual information • title • author's name • description Image Formats JPEG • Standard method of compressing photographic • Widely used image format • Joint Photographic Experts Group • Compression is lossy • allows the user to set a desired level of quality • For a Quality factor 75%, JPEG achieves image size around 6% of original size Image Formats - JPEG JPEG Preprocessing 1. partition the image into blocks of size 8 x 8 pixels 2. subtract 127 from each pixel intensity in each block Image Formats - JPEG JPEG DCT Preprocessing Discrete Cosine Transformation Transformation Image Formats - JPEG JPEG Preprocessing Transformation make decisions about values in the transformed image Quantization • elements near zero will converted to zero • All quantized values will then be rounded to nearest integers. Image Formats - JPEG JPEG Preprocessing Transformation Quantization quantization matrix for a quality of 50% Image Formats - JPEG JPEG • Huffman coding algorithm Preprocessing The original image: 1602408 = 307,200 bits Coded image: Transformation 85,143 bits ~70% less storage space than that of the Quantization original image! Encoding Original Compressed Image Formats - JPEG JPEG Issues and Problems • Decoupling • Loss of information Original Compressed Image Formats - JPEG JPEG What about colors? • convert the RGB space channels to YCbCr space • each color component as would be compressed as a separate image. Image Formats TIFF • Tagged Image File Format • Developed by Aldus Corporation in the 1980s • Support for attachment of additional info. (Tag) • was originally a lossless format • platform independent • universal to software programs • can store many different types of images • are divided into sections with a different data type Image Formats Other formats • EXIF (Exchange Image File) • WMF (Windows Meta File) • BMP (BitMaP) • PTM (Polynomial Texture Mapping).

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Free Lossless Image Format
FREE LOSSLESS IMAGE FORMAT Jon Sneyers and Pieter Wuille [email protected] [email protected] Cloudinary Blockstream ICIP 2016, September 26th DON’T WE HAVE ENOUGH IMAGE FORMATS ALREADY? • JPEG, PNG, GIF, WebP, JPEG 2000, JPEG XR, JPEG-LS, JBIG(2), APNG, MNG, BPG, TIFF, BMP, TGA, PCX, PBM/PGM/PPM, PAM, … • Obligatory XKCD comic: YES, BUT… • There are many kinds of images: photographs, medical images, diagrams, plots, maps, line art, paintings, comics, logos, game graphics, textures, rendered scenes, scanned documents, screenshots, … EVERYTHING SUCKS AT SOMETHING • None of the existing formats works well on all kinds of images. • JPEG / JP2 / JXR is great for photographs, but… • PNG / GIF is great for line art, but… • WebP: basically two totally different formats • Lossy WebP: somewhat better than (moz)JPEG • Lossless WebP: somewhat better than PNG • They are both .webp, but you still have to pick the format GOAL: ONE FORMAT THAT COMPRESSES ALL IMAGES WELL EXPERIMENTAL RESULTS Corpus Lossless formats JPEG* (bit depth) FLIF FLIF* WebP BPG PNG PNG* JP2* JXR JLS 100% 90% interlaced PNGs, we used OptiPNG [21]. For BPG we used [4] 8 1.002 1.000 1.234 1.318 1.480 2.108 1.253 1.676 1.242 1.054 0.302 the options -m 9 -e jctvc; for WebP we used -m 6 -q [4] 16 1.017 1.000 / / 1.414 1.502 1.012 2.011 1.111 / / 100. For the other formats we used default lossless options. [5] 8 1.032 1.000 1.099 1.163 1.429 1.664 1.097 1.248 1.500 1.017 0.302� [6] 8 1.003 1.000 1.040 1.081 1.282 1.441 1.074 1.168 1.225 0.980 0.263 Figure 4 shows the results; see [22] for more details.
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Understanding Image Formats And When to Use Them Are you familiar with the extensions after your images? There are so many image formats that it’s so easy to get confused! File extensions like .jpeg, .bmp, .gif, and more can be seen after an image’s file name. Most of us disregard it, thinking there is no significance regarding these image formats. These are all different and not cross‐ compatible. These image formats have their own pros and cons. They were created for specific, yet different purposes. What’s the difference, and when is each format appropriate to use? Every graphic you see online is an image file. Most everything you see printed on paper, plastic or a t‐shirt came from an image file. These files come in a variety of formats, and each is optimized for a specific use. Using the right type for the right job means your design will come out picture perfect and just how you intended. The wrong format could mean a bad print or a poor web image, a giant download or a missing graphic in an email Most image files fit into one of two general categories—raster files and vector files—and each category has its own specific uses. This breakdown isn’t perfect. For example, certain formats can actually contain elements of both types. But this is a good place to start when thinking about which format to use for your projects. Raster Images Raster images are made up of a set grid of dots called pixels where each pixel is assigned a color.
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Digital Preservation Guidance Note: 4 Graphics File Formats Digital Preservation Guidance Note 4: Graphics file formats Document Control Author: Adrian Brown, Head of Digital Preservation Research Document Reference: DPGN-04 Issue: 2 Issue Date: August 2008 ©THE NATIONAL ARCHIVES 2008 Page 2 of 15 Digital Preservation Guidance Note 4: Graphics file formats Contents 1 INTRODUCTION .....................................................................................................................4 2 TYPES OF GRAPHICS FORMAT........................................................................................4 2.1 Raster Graphics ...............................................................................................................4 2.1.1 Colour Depth ............................................................................................................5 2.1.2 Colour Spaces and Palettes ..................................................................................5 2.1.3 Transparency............................................................................................................6 2.1.4 Interlacing..................................................................................................................6 2.1.5 Compression ............................................................................................................7 2.2 Vector Graphics ...............................................................................................................7 2.3 Metafiles............................................................................................................................7
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Digital Preservation Guidance Note: 4 Graphics File Formats Digital Preservation Guidance Note 4: Graphics file formats Document Control Author: Adrian Brown, Head of Digital Preservation Research Document Reference: DPGN-04 Issue: 2 Issue Date: August 2008 ©THE NATIONAL ARCHIVES 2008 Page 2 of 15 Digital Preservation Guidance Note 4: Graphics file formats Contents 1 INTRODUCTION .....................................................................................................................4 2 TYPES OF GRAPHICS FORMAT........................................................................................4 2.1 Raster Graphics ...............................................................................................................4 2.1.1 Colour Depth ............................................................................................................5 2.1.2 Colour Spaces and Palettes ..................................................................................5 2.1.3 Transparency............................................................................................................6 2.1.4 Interlacing..................................................................................................................6 2.1.5 Compression ............................................................................................................7 2.2 Vector Graphics ...............................................................................................................7 2.3 Metafiles............................................................................................................................7
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Free Lossless Image Format Based on MANIAC Compression
FLIF: FREE LOSSLESS IMAGE FORMAT BASED ON MANIAC COMPRESSION Jon Sneyers Pieter Wuille Cloudinary Ltd. Blockstream [email protected] [email protected] ABSTRACT think of a poster that contains a photo combined with text el- We present a novel lossless image compression algorithm. ements, or a satelite image annotated with labels and arrows. It achieves better compression than popular lossless image 2) It is not easy to explain to non-technically oriented formats like PNG and lossless JPEG 2000. Existing image users when to use which image format (and which compres- formats have speciﬁc strengths and weaknesses: e.g. JPEG sion parameters). It would be more user-friendly and less works well for photographs, PNG works well for line draw- error-prone to have only one format that “just works”. ings or images with few distinct colors. For any type of im- 3) Many devices, applications, and web services only sup- age, our method performs as good or better (on average) than port one (or a few) image formats. As a result, sometimes any of the existing image formats for lossless compression. users are forced to use suboptimal image formats. Interlacing is improved compared to PNG, making the format 4) Lossy compression by deﬁnition means that informa- suitable for progressive decoding and responsive web design. tion is lost, and the sender of the image has to decide how much Index Terms information gets lost. However, it is the receiver of the — Digital images, compression algorithms image who knows best what level of information loss (if any) is “acceptable” for their intended use of the image.
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Lecture 03 Bitmap Image Formats
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