Why are there so many different image formats on the Web?

It certainly is true that there are lots of different image formats on the web. The two most common by far are GIF (Graphics Interchange Format) and JPEG (Joint Photographic Experts Group) files. Both of these formats encode static (as opposed to animated) bitmap images.

In a bitmap image, the image file has to define the exact color of every pixel in the image. Bitmaps use a grid of colors known as pixels to represent images. Each pixel is assigned a specific location and color value. Bitmap images are the most common electronic medium for continuous-tone images, such as photographs or digital paintings, because they can represent subtle gradations of shades and color. Bitmap images are resolution dependent - that is, they contain a fixed number of pixels. As a result, they can lose detail and appear jagged if they are scaled on-screen or if they are printed at a lower resolution than they were created for. That would be a huge image file, so both the GIF and JPG formats compress the image in different ways. In a GIF image, the number of colors is reduced to 256 and then "runs" of same-color pixels are encoded in a color+numberOfPixels format.

A JPG file uses a much more complex technique to compress images, like photographs, where the color of every pixel is different. A GIF file creates a perfect reproduction of the original, while a JPG does not. An animated GIF is a sequence of GIF files all bonded together and displayed one after the other. With enough panes, you can get very realistic animations. However, the size of the file is the sum of the GIF files used to create the sequence, and that can add up quickly. GIF format is suitable for storing graphics with relatively few colors such as simple diagrams, shapes, logos and cartoon style images.

An MPEG (Moving Picture Experts Group) file uses a complex algorithm like a JPEG file does - it tries to eliminate repetition between frames to significantly compress video information. In addition it allows a soundtrack (which animated GIFs do not). Because a typical sequence has hundreds or thousands of frames, file sizes can still get quite large.

Shockwave provides a vector-based animation capability. Instead of specifying the color of every pixel, a Shockwave file specifies the coordinates of shapes (things like lines, rectangles, circles, etc.) as well as the color of each shape. Shockwave files can be extremely small. They allow animation and sound. The images are also scalable - because they are vector-based, you can enlarge the image and it will still look great.

Finally there are the NxView files. These are vector-based 3D files that allow user interaction. You can rotate and zoom in on a 3-D object in any way you like. This is essentially the Shockwave idea taken to 3-D. The files are suprisingly small (100K to 200K) for the amount of detail they contain.

(based on:http://computer.howstuffworks.com)

12. Find English equivalents in the text:

Растрове зображення, карта кольорів, безперервний тон, тонка градація, роздільна здатність, стискати, зменшений, з’єднані один з одним, вікна, придатний, усувати, прямокутник, масштабований, обертати, збільшити (2).

13. Answer the questions:

What are the two most common image formats on the web?
What images do GIF and JPEG encode?
What is characteristic for a bitmap image?
What is an animated GIF?
What is GIF format suitable for?
What does an MPEG (Moving Picture Experts Group) file use?
What does a Shockwave file specify?
What files allow user interaction?

14. In pairs, discuss these questions:

Why do companies have websites?

What is the difference between a website and a web page?

What is a home page?

Do you have a blog or personal website? Describe it.

15. Read and translate the text. Learn the words in bold type:

Читайте також:

<== попередня сторінка	\|	наступна сторінка ==>
How a game is made?	\|	Creating a website

Не знайшли потрібну інформацію? Скористайтесь пошуком google:

Генерація сторінки за: 0.006 сек.