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Understanding Image Size and Storage

Understanding Image Size and Storage. Web Animation and Graphics (MIT3449) Bavy LI. What is Adobe Photoshop?. Adobe Photoshop is a robust image editing application used on the Mac and/or the PC .

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Understanding Image Size and Storage

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  1. Understanding Image Size and Storage Web Animation and Graphics (MIT3449) Bavy LI

  2. What is Adobe Photoshop? • Adobe Photoshop is a robust image editing application used on the Mac and/or the PC. • It is geared towards the editing of Photographs, but continues to push the boundaries of image manipulation. • Can be used to create a wide variety of images for both print and on the World Wide Web.

  3. Image Size and Resolution • Image Resolution • The fineness of detail in a digital image. • Image Size and Resolution • If the number of pixels stays the same in an image, then, as the size of the image increases, the resolution (fineness of detail) decreases.

  4. Images • Images which are intended to stay on screen, need to be a low resolution. Why? Because monitors only have a resolution of 72dpi, a resolution considerably higher isn’t able to be displayed. • Images which are intended for printing, need to be a high resolution. The printed image and the on-screen image are completely different entities. An image printed at 72dpi will be a low quality image.

  5. Image Resolution • The number of pixels in a linear inch (ppi) is called image resolution. • The more ppi, the higher the image resolution, and the larger the file size. • The standard screen resolution is 72 ppi. • Images used for the Web should have an image resolution of 72 ppi.

  6. Image Resolution • Standard • For web graphics 72 – 90 dpi (dots per inch) • For print graphics 300 lpi (lines per inch)

  7. Pixels and DPI • Pixels (picture elements) • The individual dots that are used to display an image on a computer monitor. “The higher the resolution, the more pixels.” • DPI (dots per inch) • A unit that is used to measure the resolution of a printer or image-setter. • DPI is sometimes used to describe the input resolution of a scanner, but PPI is the more accurate term.

  8. Screen Resolution • Your images will be displayed differently depending on your screen resolution. • 640 x 480 • 800 x 600 • 1224 x 768 • Demonstration on checking/changing your screen size.

  9. Storage • Storage • RAM (Random Access Memory) • The system memory of a computer that is used for running an application and processing information, and for temporary storage. • Zip Disk – 100 Megabytes • Floppy Disk – 1.4 Megabytes • CD-ROM – Approx 600 Megabytes

  10. File Size • Standard units of measurement • Bit • Byte (8 bits) • Kilobyte • Megabyte • Gigabyte • For every 1000 Bytes there is 1 Kilobyte • For every 1000 Kilobytes there is 1Mebgabyte • For every 1000 Megabytes there is 1 Gigabyte The true unit of measure is 1024 bytes, for simplicity we are rounding to 1000 so that we can quickly do the math.

  11. File Size What file size is bigger? • 2.6 Megabytes • 2600 Kilobytes They are basically the same

  12. Graphic File Formats • GIF – Graphics Interchange Format. Limited to 8 bit, 256 colors. Used for large areas of uniform color. Lossless compression. 2/3rds compression: 96KB = 64KB. Can assign one color as transparent, can also use animation. • JPEG – Joint Photographers Experts Group. The best platform for photographic images; textures and gradations. A compression method in Photoshop that shrinks a file's storage size. • TIFF – Tagged Image File Format.A common format that is used for saving a bitmapped image, such as a scan. A TIFF image can be colors separated and can contain colors management profiles. Used for magazine, high quality images . • PICT – Mac native file format

  13. Graphic File Formats • PSD • Photoshop file is the only format in which multiple layers and layer transparency are available. PSD’s are large files. • BMP • Large file, standard windows format, not compressed • PNG • New format, good for alpha channel masking to Flash

  14. Creating an Image Archive • Be sure to maintain the original file. • It is best to create your graphics files in TIFF or PICT whenever possible.  • Then save the file as a JPEG or GIF format for web publishing.

  15. Vector vs. Bitmap: Graphic Formats • Vector • Smaller file size • Easy resizing of an image • no distortion • Bitmap • Pixel based image

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