Graphics

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Graphics

  1. 1. Graphic Image File. Indexed color file, for raster (pixmap) data only. Primarily for synthetic, somewhat flat images such as logos, diagrams, navigation buttons, etc. Technically GIF and its LZW compression algorithm are ―lossless,‖ but since it supports indexed color only (8-bit or less), you often have to permanently throw away image data prior to (or in the process of) exporting your master file as a GIF. Don’t be confused by Photoshop’s Save for Web options for GIF, where you’ll see a ―lossy‖ checkbox: that just rearranges the pixel patterns slightly, prior to exporting the GIF, to enhance the compression. GIF being a ―lossless‖ format means that, unlike with JPEGs (a lossy format), you could possibly open a GIF repeatedly, edit it, and re-save it back out again without necessarily degrading it. That’s not ideal, unless you really know what you’re doing. It’s generally best to go back to the master file — often a PSD — for editing, and then re-export the GIF.
  2. 2. GIF is my best Web option for images with flat, solid colors — the sort of images one normally create in vector drawing programs such as Illustrator. Of course I love to put my Illustrator images on the Web in their original vector form, but for the most part that is not possible (but see SVG lower down in this table). So I export our vectors to raster formats like GIF or PNG for the Web.
  3. 3. JPEG Joint Photographic Experts Group. Compressed, lossy file format, for raster (pixmap) data only. Mostly for phototype images on the Web. Can hold RGB data; many compression levels and other options available.  Also be careful not to edit JPEG files if at all possible; go back to the original master file (PSD, TIFF, or whatever) for editing and then re-export a new JPEG with your changes. JPEG compression always involves data loss and degradation; editing JPEGs is just corrupting the corruption — it’s degrading!
  4. 4. I have to be careful not to edit JPEG files if at all possible; go back to the original master file (PSD, TIFF, or whatever) for editing and then reexport a new JPEG with my changes. JPEG compression always involves data loss and degradation; editing JPEGs is just corrupting the corruption — it’s degrading!
  5. 5.   Portable Network Graphics. The newest of the three major Web graphics file formats, with more features than GIF or JPEG. PNG’s use is growing slowly over time, especially as newer browsers come into play. It’s already a reasonable replacement for many GIFs (but not for animated GIFs); but for photo-type images, JPEG will usually be more efficient.
  6. 6. Lossless compression which means I could use it as an editable format, although I probably should not in most cases. Multi-bit transparency map (alpha channel), even for photo-type images. Metadata for color management (gamma and ICC color profile), although this is something of a tease since most browsers do not support those things. Can hold either RGB data (like a JPEG) or indexedcolor data (like a GIF) — but not CMYK, since that is designed for the Web, not for print.
  7. 7. Scalable Vector Graphics. Attempt to introduce a standard vector format for the Web. Wouldn't you love to put flat-color or other simple graphics (like logos and diagrams) online in compact, scalable vector form? The W3C has approved this Adobe-sponsored XML derivative. Not really usable yet in most real-world projects, because browser support is still spotty — but improving. The only Web vector format widely used at present is to embed images in Flash, but that’s not really a substitute for SVG (you wouldn’t create a Flash file just to hold a non-animated scalable logo, for example).
  8. 8. Using SVG would not be a suitable option for me at this time because browser support is spotty.
  9. 9. PostScript is a page-description language that some programs can generate and some printers (the expensive kind) can print from. A .ps is a simple text file that results when you tell a program to send its PostScript instructions to a file on your hard drive instead of to a printer; it’s therefore called a ―print to disk file.‖ (It’s also sometimes called a ―pure PostScript file‖ or a ―PostScript dump.‖)
  10. 10. There are basically three things I can do with a .ps file: send it to a printer which should then print the original page, not the PostScript text convert it to PDF via Acrobat Distiller or if I had a PostScript programmer edit it directly in a text editor. I am not a PostScript programmer but, being rather geeky for a creative type, I would have to be able to make some simple, useful changes within .ps files on occasion. As with any programming code, I have to be careful one tiny mistake and the whole thing may not work.
  11. 11. Encapsulated PostScript. A useful but flaky extension of the basic PostScript file Encapsulated PostScript. EPS is essentially a PostScript file in an ―envelope.‖ It usually — but not always — includes a rasterized preview in TIFF or PICT, plus some metadata. EPS was originally the native format of Illustrator, back in the primordial days of PostScript..
  12. 12. Pros: can contain clipping path, true font data, various kinds of metadata; widely accepted. Cons: previews optional & nonstandard; sometimes contains insufficient data but you wouldn’t know because the preview can be misleading; file format has evolved so is nonstandard; may only print properly to PostScript printers; can be flaky at times.
  13. 13.  Adobe Illustrator's proprietary file format — closely related to, but not the same as, EPS.  The Adobe Illustrator program’s proprietary format originally was EPS. Illustrator’s current .ai format is essentially an extension of that original EPS format, broadened to accommodate Illustrator’s newer capabilities. A few other programs may support .ai files, but it’s a moving target as Illustrator evolves. Most other programs stick to the original, more generic form (EPS).
  14. 14. AI has about the same as EPS , so the Pros and Cons are about the same Pros: can contain clipping path, true font data, various kinds of metadata; widely accepted. Cons: previews optional & nonstandard; sometimes contains insufficient data but you wouldn’t know because the preview can be misleading; file format has evolved so is nonstandard; may only print properly to PostScript printers; can be flaky at times.
  15. 15.  Portable Document Format, also known as ―Adobe Acrobat format. Adobe has been slowly moving towards PDF as a universal file format (especially within its own product line), but it’s not clear whether it will ever replace most proprietary and generic graphic file formats. You might like to visit Adobe’s PDF Tech Center online. Still to come: discussion of prepress variants of PDF with more specific specs: PDF/X-1a PDF/X-3
  16. 16. Cons: Content formatted for Print – A PDF file is usually formatted to the size of a printed page like A4 or Letter, not to the size of a screen. This makes it difficult to read online as the user needs to spend more time scrolling through the content as they read. Most PDF files have been converted from a document format and as such, are long and boring to read in an online environment. Pros: Protecting Intellectual Property – If you have a portion of content that you do not want copied by visitors, then PDF is the way to go. This format also enables the creator to insert information that stays with the content so readers always know exactly where it came from.
  17. 17. PSD stands for ―Photoshop document.‖ It’s an application-specific proprietary format, but because of Photoshop’s dominant position in the pixel-editing world, PSD has become something of a quasi-standard. A number of other programs, even some that don’t come from Adobe, support PSD as an additional file format — but usually as read-only or for import/export purposes, not as their true
  18. 18. Pros: Changes are a lot faster (including changes to colors, and to some extent to fonts). When you're laying the page out as HTML, you're showing the client something a lot closer to what the final product will look like. They can see the effects of a liquid layout by changing the size of the window. Cons: Not all visual designers can create a mockup in HTML. It will have to be a two person task. An HTML person and a Photoshop person.
  19. 19. A newer (and basically unrelated) meaning of ―raw‖ — more formally called Camera Raw — has become very common with the rise of digital photography. Some midrange, and all high-end, digital cameras have the ability to save images with no lossy compression (as opposed to the JPEGs that are more common as a digital camera format). Essentially, they’re saving the full information that their sensors capture. Camera Raw isn’t really a file format in the conventional sense because each brand of camera structures the data differently, and expects you to read the data (or transfer it to your computer), and perhaps edit it as well, using their own software. I suspect the lock-in is intentional, and of course it’s bad for consumers.
  20. 20. Pro: Raw files contain the full, unaltered information as taken off the sensor, while in RGB (TIFF or JPEG) ones this information is already converted, for better or worse, using the current camera settings. Performing that conversion on a PC, you can use more powerful and/or most up-to-date software, possibly better than the camera firmware. Cons: With raw files you need to do the conversion before you can edit, print, or even view your images; an extra step.
  21. 21. Tagged Image File Format. Raster only. Most widely used format for photos in prepress world (although EPS is also used for this purpose). Cross-platform. There are many variations of TIFF — in fact, it’s really a whole family of file formats — and you can’t assume that a program that “supports TIFF” will understand all of them. Variations include compressed (lossless LZW, or other methods) vs. uncompressed; RGB vs. CMYK; 24 bit vs. 48 bit; and a variety of TIFF-based alternative file formats, such as TIFF IT (widely used by ad agencies). TIFF is really designed for use by professional graphic designers. Although the format itself is relatively trouble-free, the numerous variations are likely to confuse nonprofessionals trying to match individual TIFFs to the programs and processes that support them.
  22. 22. Pros: most reliable, widespread format for raster data. Can hold almost any resolution, color scheme, etc. I like this format because it’s uncomplicated and (unlike EPS) rarely causes trouble. Cons: can’t hold vector data; large, and sometimes slow to print; Mac and PC have slightly different flavors (although most Mac apps support both); many nonstandard ―improved‖ versions floating around.
  23. 23. Common but Windows-only raster format. BMP is very common in the Windows world, but is not crossplatform. It’s not supported by professional prepress processes or by Web browsers, and so is only appropriate for internal use within the local Windows environment.
  24. 24. Pros: Bitmap files may be easily created from existing pixel data stored in an array in memory. Retrieving pixel data stored in a bitmap file may often be accomplished by using a set of coordinates that allows the data to be conceptualized as a grid. Pixel values may be modified individually or as large groups by altering a palette if present. Bitmap files may translate well to dot-format output devices such as CRTs and printers. Cons: They can be very large, particularly if the image contains a large number of colors. Data compression can shrink the size of pixel data, but the data must be expanded before it can be used, and this can slow down the reading and rendering process considerably. Also, the more complex a bitmap image (large number of colors and minute detail), the less efficient the compression process will be.
  25. 25. Unlike JPEGs, GIFs, and BMP images, vector graphics are not made up of a grid of pixels. Instead, vector graphics are comprised of paths, which are defined by a start and end point, along with other points, curves, and angles along the way. A path can be a line, a square, a triangle, or a curvy shape. These paths can be used to create simple drawings or complex diagrams. Paths are even used to define the characters of specific typefaces.
  26. 26. Pros: Vector files are useful for storing images composed of line-based elements such as lines and polygons, or those that can be decomposed into simple geometrical objects, such as text. More sophisticated formats can also store 3D objects such as polyhedrons and wire-frame models. Vector data can be easily scaled and otherwise manipulated to accommodate the resolution of a spectrum of output devices. Cons: Vector files cannot easily be used to store extremely complex images, such as some photographs, where color information is paramount and may vary on a pixel-by-pixel basis. The appearance of vector images can vary considerably depending upon the application interpreting the image. Factors include the rendering application's compatibility with the creator application and the sophistication of its toolkit of geometric primitives and drawing operations.
  27. 27. Most images you see on your computer screen are raster graphics. Pictures found on the Web and photos you import from your digital camera are raster graphics. They are made up of grid of pixels, commonly referred to as a bitmap. The larger the image, the more disk space the image file will take up. For example, a 640 x 480 image requires information to be stored for 307,200 pixels, while a 3072 x 2048 image (from a 6.3 Megapixel digital camera) needs to store information for a whopping 6,291,456 pixels.
  28. 28. Pros: The geographic location of each cell is implied by its position in the cell matrix. Accordingly, other than an origin point, e.g. bottom left corner, no geographic coordinates are stored. Due to the nature of the data storage technique data analysis is usually easy to program and quick to perform. Cons: The cell size determines the resolution at which the data is represented. It is especially difficult to adequately represent linear features depending on the cell resolution. Accordingly, network linkages are difficult to establish.

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