With no compression the file size would be 20020031024 117 KB Same image save

With no compression the file size would be

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With no compression the file size would be: 200*200*3/1024 = 117 KB Same image, save as a gif: With 256 Colours 8.4 KB With 16 Colours (cant pick less than 9 in Photoshop) 5 KB NOTICE: NO CHANGE IN QUALITY, LOSSLESS COMPRESSION! Slide 23 of 48 GIF Not great for photography because can only store 256 colours. QUESTION: Can you tell which image has fewer colours? GIF Transparency One Colour Transparency Allows for transparency of ONE colour Background will show through: Question: Can you see the problem with this type of transparency?
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10/3/2019 5 Slide 25 of 48 GIF Animation Allows for animation Don’t need a plug in for gif animation! Works in all browsers, universal format! Slide 26 of 48 GIF Dithering Allows for dithering : Question : What do you think a program, that converts images into gifs does, if the image has more than 256 colors? Solution 1 : Substitute one of the colors you have for one of the colors you are missing Solution 2: Any guesses? HINT: What did you do when you were a kid and your parent gave you red and blue and yellow and black play-doh? you didn’t realize it but you were using a 2 -bit color depth play-doh palette = 2 2 = 4 colors GIF Dithering Juxtaposing (place side by side) pixels of two colors to create the illusion that a third color is present (grainy look) Example: Slide 28 of 48 Another Example of Dithering Slide 29 of 48 GIF Dithering You can reduce the number of colors in a GIF and choose options to control the way colors dither in the application or in a browser. Slide 30 of 48 GIF Dithering Original Image Dithering in Photoshop, used 64 colours to make the differences show up more to the naked eye!
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10/3/2019 6 Slide 31 of 48 GIF Interlacing How images are downloaded to your screen Interlacing lets you have a feel for the whole picture, you don’t have to wait around to see it download (good for dial up connections) A process by which the image is drawn in a series of passes rather than all at the same time (file size bigger) Slide 32 of 48 GIF Compression Can compress more by reducing the number of colours in the image: Colour Resolution Size (KB) % Decreased 256 28483 128 23141 19 64 19488 32 32 15903 44 16 11863 58 8 8886 69 Slide 33 of 48 GIF Slide 34 of 48 JPG (JPEG) Joint Photographic Experts Group Widely used on the World Wide Web Cross Platform (works on Macs, Windows) Supports 24 bit colour Question : How many colours can you have in a JPG file if it allows for 24 bit colour? Great for photographs Larger file sizes than GIFs BUT allows for a full colour scheme! Slide 35 of 48 JPG Good for photographs, computer games, screenshots, stills from a movie, etc. Best for blends of color, softer shadow effects, subtle changes in color Not good for well-defined lines or sharp contrasts between colours Question : Guess which one is the GIF and which one is the JPG: Slide 36 of 48 JPG Notice what happened to Homer when the original GIF was resaved as a JPG:
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10/3/2019 7 Slide 37 of 48 JPG JPG does a lossy compression
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