Image Basics

Most of the images you can see in the Net, download or import from a camera are so called raster images. That means that the image is made up of thousands of small dots known as pixels.

Image Basics

The size of a raster image is most commonly expressed in terms of its dimensions, such as 500 X 700 (500 dots wide and 700 dots tall). When you’re shopping for a digital camera, its quality setting is described in terms of the total number of pixels in the images. Expressed this way, 500 X 700 image would be described as 1.2 megapixels, where mega means one million. The assumption that the more pixels the image contains, the better it can look, is quite obvious, but in real life images of any size can be of poor quality.

Formats and Compression

There is a wide range of image file formats, each of which has its own advantages and disadvantages.

Most of the images you can find browsing the net, are in compressed formats. That means they are considerably reduced in terms of bytes but only marginally reduce the quality. Experts advice against over-compress images, as they look terrible. When saving an image, you should strike a balance between quality and file size.

  • JPEG format (short for Joint Photographic Experts Group) is the most common picture format of all. It’s the default file type for most digital cameras. When saving a JPEG, the user can choose from a sliding scale of compression.
  • GIF format (short for Graphics Interchange Format) is also very common. This format is considered better for images with large areas of flat color (f.e., graphics rather than photographs). This format allows slide-show-style animations and transparent backgrounds, both widely used online.
  • PNG (short for Portable Network Graphics) has a better transparency abilities than GIF or JPEG. This format is more likely used to create screenshots, etc.
  • RAW is a non-compressed format used in digital photography or image editing. Different cameras use different RAW formats, but all of them are quite better than JPEG format in terms of quality. The difference, however, is very important for people who are eager to get seriously into digital photography.
  • TIFF (Tagged Image File Format) is non-compressed format most commonly used by professionals to work with their photographs and graphics. Many scanners and cameras also generate TIFFs. In fact, TIFF can be compressed, but usually it isn’t.

You can find other image file formats, such as BMP, PICT, TGA, EPS, etc. Most of them can be open in alternate format.

To Download Pics

You can download or import images on your computer form many external sources, starting from websites. You can use webcams, scanners, mobile phones and other sources :

Digital camera allow you to import pics very easily. Generally, no special software is needed to import images from a digital camera to your computer.

The Web: To download an image you can click it, copy and paste on your machine, otherwise, simply drag it from the browser window onto the desktop or into a folder. You can also right-click the image and choose Save image As from the context menu.

Flatbed scanners: It is possible to import a copy of a photograph with a scanner, that’s you’ll have a digitalized copy of a photograph, a magazine page or anything else two-dimensional.

Mobile phone: Mobiles phones are easy enough to transfer documents wirelessly to your computer. You should pair your computer and your phone, trigger your image transfers from the mobile and wait for a few seconds.

Screen grabs or Screenshots: This is a snapshot of whatever you can see on your screen at a specific moment. The screen grabs are useful for everything, from capturing a weird error in order to send it to someone for troubleshooting advice, or to quickly capture the information displaying on various windows in a format easy to open.

From scratch: Users can create images very easily using drawing software o a photo editing programs, such as Gimp or Photoshop (Photoshop is designed for editing pixel-based images that already exist, and tampering with one or more pixels simultaneously). As to drawing programs, the are so called vector-based drawing programs that, instead of pixels, let the user work with editable lines and shapes, editing the lines, texts, shapes, colors… Once the image is ready, the user can export it in a standard pixel-based format and treat it just like and other image. Adobe Illustrator, part of the Creative Suite package.

Previewing, Converting, Resizing Images

If you have right tools, it’s easy to change an image from one format to another, as well as to change its size in pixels or add compression. It may be useful and it may be essential as not every program will recognize every file format, so sometimes you may need to convert the form to open a particular image in a particular application.

Miscellaneous

Google Image Search (images.google.com) offers an easy way to fish for images online: You can use the size options to filter out pics that are toss small for your need. Grab the full size version of the image, not the thumbnail  preview on the search page.

Links

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