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Image & Graphic Files


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Image & Graphic Files

  1. 1. Image & Graphic Files Susan Daun Deena Patel Felicity Skipper Hasan Yaqub
  2. 2. Vector vs. Bitmap based images <ul><li>VECTOR BASED </li></ul><ul><li>Advantages: </li></ul><ul><ul><li>Based on mathematical formulae which means they are easily scalable . </li></ul></ul><ul><ul><li>contains only the defining mathematical formulas for each element within the image and therefore requires less space in which to be stored </li></ul></ul><ul><ul><li>Usually contain well defined curves and shapes </li></ul></ul><ul><li>Disadvantages: </li></ul><ul><ul><li>cannot be used for photo-realistic images because these images do not tend to contain well defined lines. </li></ul></ul><ul><li>File names for vector-based images usually consist of extensions such as *.EPS , *.AI , *CDR , or *.DWG . </li></ul><ul><li>BITMAP BASED </li></ul><ul><li>Advantages: </li></ul><ul><ul><li>More suitable for photo-realistic images that require complex colour scales. </li></ul></ul><ul><ul><li>Each bitmap-based image is mapped into a grid. The size of the grid is based on the image's resolution. A bitmap-based image is like a mosaic of pixels with each pixel holding a specific colour. </li></ul></ul><ul><li>Disadvantages: </li></ul><ul><ul><li>Not easily scalable because each image is mapped onto a non-flexible grid . Enlarging the image would disrupt the grid causing lines to become blurry. </li></ul></ul><ul><ul><li>Require more computer memory for file storage (compared to vector based images) </li></ul></ul><ul><ul><li>File names for bitmap-based images usually consist of extensions such as *.PSD , *.JPG , *GIF , *.TIF , or *.BMP . </li></ul></ul>
  3. 3. GIF vs. JPEG <ul><li>GIF is commonly used as an image format for internet graphics. This format limits the number of colours used in an image to 256. For this reason, this type of format is most suitable for images with solid colours as oppose to photo realistic image which contain expansive colour ranges. </li></ul><ul><li>JPEG format is also commonly used for internet graphics. However, this file format does not contain a specific number of colours within the ranges and is therefore suitable for use with photo-realistic images with large colour ranges . </li></ul>
  4. 4. Embedded vs. Linked Graphics <ul><li>A linked image remains outside of the document , with a pointer in the document linked to the external image. </li></ul><ul><li>An embedded image is stored inside the document itself, with no link to any external image. </li></ul><ul><li>The default is the linked image. This is because embedded images are generally treated as spam by incoming spam filters. Also viruses can be put onto embedded images. This means that linking images is much safer than embedding them . </li></ul>
  5. 5. Colour Palette <ul><li>A palette is a subset of the total range of colours supported by a computer graphics system . Each colour in the palette is assigned a number, and for each pixel, one of these numbers is stored. This number determines the colour of the pixel. </li></ul><ul><li>A palette may also refer to a small window, or section of a window that's readily accessible for quick and frequent colour choices </li></ul><ul><li>Small colour pallette example is a GIF file </li></ul><ul><li>Large colour pallette example is a TIFF file </li></ul>
  6. 6. Lossless Compression <ul><li>Lossless Compression allows an image to be reversibly compressed and then retrieved at the same quality as the original. </li></ul><ul><li>It is used in many applications such as the ZIP file format and is useful for medical images that need to be viewed at a high quality. </li></ul><ul><li>In contrast to this JPEG is a lossy data compression technique, as the reconstructed image is not exactly the same as the original. Excess data can be lost because the human eye is not sensitive enough to notice. </li></ul>
  7. 7. PNG Files <ul><li>One problem with using JPEG files is that text can become blurred when it is saved in this format and because GIF files have a limited number of colours images can have a lower quality at higher resolutions. </li></ul><ul><li>The Faculty Skills Guide says that “to overcome these issues files can be saved to PNG format”. </li></ul>
  8. 8. Disadvantages of .bmp files <ul><li>One of the disadvantages of bitmap graphics, is that they do not scale very well . </li></ul><ul><li>If the image is made larger or smaller, then the program has to try and recalculate what colour the pixels should now be. </li></ul><ul><li>Reducing the size of a bitmap also distorts the original image because pixels are removed to reduce the overall image size. </li></ul><ul><li>If the bitmap image is enlarged too much, we will also run into the problem of aliasing, this is the staircase effect, that usually shows up in diagonal lines, or where two different colours sit side by side. The image will also start to look blurred . </li></ul>
  9. 9. Flickr <ul><li>Flickr is a photo sharing website and web services suite, and an online community platform. </li></ul><ul><li>In addition to being a popular Web site for users to share personal photographs, the service is widely used by bloggers as a photo repository. Its popularity has been fueled by its innovative online community tools that allow photos to be tagged and browsed. </li></ul><ul><li>Flickr is the best way to store, sort, search and share your photos online. It helps you organize that huge mass of photos you have and offers a way for you and your friends and family to tell stories about them. (Flickr is therefore mainly used for recreational purposes). </li></ul>