Discards more data about colours than about brightness Not all of the

Discards more data about colours than about

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Discards more data about colours than about brightness Not all of the information in the original image is preserved not the same as the original Degrades the image quality Compression is achieved by ‘forgetting’ certain details about the image, which the JPG will then try to fill in later when it is being displayed Degree of amount of information LOST (lossyness) can be varied by adjusting compression parameters. (controlled by you) Because image data is lost with each compression, work with the image in native format, and when ready with final product, save it as a .jpg file Slide 38 of 48 JPG Quality of image is inversely proportional to amount of compression A higher image quality setting (has a lower compression value) results in less data being discarded. Original 0% Compression = 100% Quality Slide 39 of 48 JPG Can you tell which image was saved with low quality, high compression in Photoshop? Slide 40 of 48 JPG No Transparency No Animation No Interlacing No dithering ( Question : why no dithering?) Slide 41 of 48 PNG Pronounced PING Created specifically because of licensing issues with GIFs in the 90s Does LOSSLESS compression Multiple versions of PNG PNG-8 PNG-24 PNG-32 Slide 42 of 48 PNG - 8 Similar to GIF Only allows for 256 colours Allows for 1 transparent colour Storing of colours is more efficient in PNG files than GIFS thus PNG-8 files might be SMALLER than their GIF counterparts (this is software dependent)
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10/3/2019 8 Slide 43 of 48 PNG - 24 Allows for 24 bit colour Similar to JPGs in terms of colour support It is LOSSLESS compression so JPG files will generally be smaller than the same image saved as PNG-24 file. Slide 44 of 48 PNG - 32 Some PNGs have a 32-bit colour depth What are the last 8 bits for? Allows for transparency on each pixel, with different levels of opacity. Uses RGBA model (A stands for Alpha). Comparison of GIF, JPG, PNG GIF JPG PNG-8 PNG-24 Best For Logos, Cartoons, Drawings Photographs Logos, Cartoons, Drawings Photograph Images with a need for transparency Type of Compression Lossless Lossy Lossless Lossless Well Supported in Browsers All All All Not on IE6 Transparency One COLOUR only NO One COLOUR only Varying levels of opacity and transparency Animation Yes No No No Dithering Yes No Yes No Interlacing Yes No Yes Yes Shape of image Must be rectangular Slide 46 of 48 File Size Comparison Things to think about when working with images: Slide 48 of 48 Review What formats would each of these images be best saved as? Left: JPG, Right: PNG or GIF
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