Learning to Work with Images, Sound, and Video

This chapter covers the tools and techniques used to produce the kinds of images, sounds, and video segments contained in the multimedia applications described throughout the book.

Use the following questions to guide your study:

• What distinguishes paint from draw programs, and what are some educational applications of each?
• Why must teachers pay attention to the file format used to store graphic images and sounds?
• How can teachers and students capture images for use in their own projects?
• How can teachers and students combine video segments and other multimedia formats into an integrated video production?
• How do students benefit from the collection and manipulation of sounds and graphics?

Tools for Creating and Manipulating Images

Images can be brought into the computer environment in several ways:

• Images can be created using technology
• Images can be captured using technology

I. Paint and draw programs (pp. 273-282)

Paint programs store images as a record of the individual dots of color. Draw programs represent images mathematically. We focus mostly on paint applications because they seem must useful for multimedia projects.

Paint programs allow students to:

• create graphics from scratch
• modify graphics generated in other ways
• save images in the format required for other applications

I.A Creating images

Paint programs allow users to produce original work. Users can create shapes, assign color to these shapes, add text, etc.

I.B Modifying existing images

Much of the chapter deals with ways technology can be used to capture images from sources external to the computer (scanner, digital camera or camcorder).

When used in association with image capture, graphic tools are used to:

• open an existing image file - this function should not be taken for granted, because the graphic tool must be able to interpret the file type used to store the image.
• modify the image in some way - e.g., add text, cut and paste parts of the image
• save the finished image in a desired format

I.C Organizing and Saving Large Image Collections.

As resources such as digital cameras make it easy to generate large numbers of images, software for organizing and labeling images becomes very useful.

I.D Comparing Paint and Draw Programs

Paint programs are used to create and manipulate bit-mapped images. A bit-mapped image is "painted" on the background by changing the color of individual pixels.

Programs used to create and manipulate "object-oriented" images are commonly called draw programs. Some differences between paint and draw programs are fairly easy to demonstrate (see image).

Because a paint program is concerned with individual pixels, it is possible to erase a portion of a square or circle created with a paint program, but not a draw program. Because the shape of a square or circle is defined mathematically in a draw program, the shapes can be resized without a change in quality (not the handles allowing modification of the shapes created in a draw program).

You may also here the term “vector graphics” used to describe the file type we are associating with draw programs. Some programs allow a paint image to be converted to a vector graphic. It is interesting to experiment with this translation. For example, Flash allows a bit-mapped image to be converted to a vectorized format. The image on the right was generating by performing this process on the image on the left. Both are presented here in jpeg format (both have again been converted to a bit-mapped format). One of the things you will note about the converted image is the lower level of fine detail. By simplifying the image, the image is easy to represent mathematically.

II. Understanding graphic file formats (pp. 282-284)

Users may encounter a variety of graphic file formats. There are several reasons for this variety:

• certain file types are more typical with certain operating systems - PICT is typically a Macintosh format and BMP is a Windows format
• certain file types are associated with certain types of application - JPG andGIF are used heavily on the web
• many graphics programs have their own native formats - the native format for Photoshop cannot be opened with the AppleWorks paint tool

Many programs have built-in translators allowing the graphics program to open several file formats. It is often useful to have access to a more expensive (high end) program, but such a program is more likely to be able to open a variety of formats and can be used to convert files from one format to another when necessary.

Web graphic formats - discussion of graphics formats for the Web

Web image compression - discussion of Web graphics compression techniques

Image resolution issues - display size and image resolution

III. Tools Capturing Still Images (pp. 284-289)

III.A Scanners (flatbed scanner)

A scanner works something like a photocopy machine. A lens and mirror system beneath a glass plate focuses the light reflected from the “original” into a charge coupled device (CCD). The CCD converts this information into a digital format and forwards the digital representation to the computer. This representation is a bit-mapped image. In those situations in which a scanner is used to capture text from a printed page, special software using what is called optical character recognition (OCR) converts words appearing within an image into a file of words.

III.B Video Digitizer

Video digitizing boards (hardware) convert an analog signal generated by a video cassette player, a camcorder, a television tuner, or a videodisc palyer into a digital signal. Video capture is accomplished by first activating a software program that accesses input from the video digitizing card. Individual images or video segments are stored.

III.C Digital Cameras

A digital camera captures images in digital format and then transfers these images to a computer. The quality of the captured image is an issue and strongly influeces the price one has to pay for a camera. Probably the most signficant factor in image quality is the density of the pixels the camera CCD is able to capture. Newer cameras, sometimes refered to as megapixel cameras, are capable of storing millions of pixels. Often, the number of megapixels (currently 1-3) provides a way to describe the quality of the camera. The high end cameras (usually costing $800-$1000) are clearly differentiated from the low end cameras (some costing less than $100). Under certain circumstances, low end cameras can provide useful images for classroom applications.

Poster Project - classroom project.

IV. Alternate Image Sources (ppp. 289-294)