A color model is a method for displaying and measuring color. The human eye perceives color according to the wavelength of the light it receives. Light containing the full color spectrum is perceived as white. When no light is present, the eye perceives black.

Two of the most common color models are:

• RGB color model (red, green, and blue), the method by which monitors display color.
• CMYK color model (cyan, magenta, yellow, and black), the method by which images are printed using the four process ink colors.

Coupled with each color model is a color gamut. The gamut of a color model is the range of colors that can be displayed or printed, with that model. The largest color gamut is that viewed in nature. The RBG gamut is smaller than the natural color gamut, and the CMYK color gamut is smaller than the RGB gamut.

Mixing three basic components of colored light in various proportions can represent a large percentage of the visible spectrum of color. These components are known as the primary colors: red, green, and blue (RGB). Because various percentages of each color are added to create new colors, the RGB color model is known as additive color. Equal amounts of red, green, and blue produce white.

All monitors display color using a mixture of the primary additive colors of red, green, and blue. As a general rule, you should edit your color images in the RGB model for the following reasons:

• RGB files are smaller than files created in other color models.
• Monitors are designed to display RGB colors best.
• The RGB color model provides a larger color spectrum than other color models on a monitor, such as CMYK.

The CMYK (cyan, magenta, yellow, and black) color model represents the four process inks used to print images on a press. To create a hard copy of an image each of four plates is inked with one of the colors. The CMYK model is called subtractive color because combining all colors subtracts color and produces black.

Resolution Principles

In broad terms, resolution refers to the unit of measurement used to determine the size of an image, the way an image is displayed on your monitor, and the device on which an image is output.

Specifically, you must consider three types of resolution when preparing images in any digital image processor like Corel PHOTO-PAINT or Adobe Photoshop:

• Image resolution refers to the size of the file in pixels, measured in pixels per inch (ppi).
• Monitor resolution determines how your image is displayed on your monitor, measured in dots per inch (dpi).
• Output device resolution determines the quality of a final printed image, which is measured in both dots per inch (dpi) and lines per inch (lpi).

Digital images are represented in pixels. Image resolution refers to the number of pixels in the image. The more pixels per square inch of the image, the higher its resolution, and subsequently, the larger the file. For example, a 1-inch square of an image scanned at 72 ppi contains 5,184 pixels (72 pixels wide x 72 pixels high), and has a file size of 6K. However, the same 1-inch square of an image scanned at 144 ppi contains 20736 pixels (144 pixels wide x 144 pixels high), and has a file size of 21K.

Monitors have a fixed resolution, determined by the manufacturer. Most Macintosh monitors display images at 72 dots per inch, and typically IBM-compatible monitors display images at 96 dots per inch.

The monitor's resolution determines the size of the image displayed on-screen, and should not be confused with image resolution. Because an image may have a higher resolution than the monitor on which it's displayed, an image with a higher resolution will appear larger on-screen than in print.

Output device resolution refers to the number of dots per inch (dpi) that the output device produces. For example, laser writers typically have a resolution of 300 or 600 dpi, and a high-quality imagesetter can print at a range between 1200 dpi and 2400 dpi or higher.

Introduction to Image Scanning

Using a scanner is the most common way of getting an image into a digital image processor such as Corel PHOTO-PAINT, Adobe Photoshop, or Microsoft Photo Editor. This section provides general information about scanning techniques to help you determine the most optimized input settings for your images.

Color Modes and File Format for Web Publication

There are two image file format that are used for distribution on the Web: GIF and JPEG.

GIF stands for Graphic Interchange Format and is a standard for digitized images compressed with the LZW algorithm, defined in 1987 by CompuServe. It is a lossless compression. Process of GIF formats production starts by converting the flat-color image to Indexed Color mode. The Indexed Color mode converts 24-bit images to 8-bit images, which display up to 256 colors. This means if the original image has more than 256 colors, all but 256 of the colors are removed from the image. However, if the original image contains fewer than 256 colors, the palette defaults to exact number of colors.

JPEG stands for Joint Photographic Experts Group; the original name of the committee that designed the standard image compression algorithm. The JPEG format is a better choice for preserving color fidelity if the original image is continuous tone (contains gradations of color or is full-color photographic image) and it is aimed towards viewers who have 24-bit monitors, which has the capacity to display millions of colors. JPEG images are subject to loss of quality due to compression. The compression option you use determines how the color information in the image is preserved (the greater the degree of compression, the greater the data loss) and the overall size of the file.

The following table shows, which file formats and color modes, should be used when preparing specific types of images for web publication.

In order to create a standard Web color pallette that works on different platforms, since the Macintosh and Windows browsers pallettes share only 216 out of 256 possible colors, the image is reduced to 216 colors, even less than in the GIF format., these two platforms.

The Following color table shows the standard Web palette of 216 colors that are common between Mac and PC platforms.

The hexadecimal values for the standard Web pallette are the true color on either platform, with no dithering and can be used with Netscape or Microsoft Internet Explorer for backgrounds colors, text colors, and link colors.

Restoring Default Preferences Using Adobe Photoshop

The Preferences file controls how palettes and command settings appear on your screen when you open Adobe Photoshop program. Each time a user quits Adobe photoshop, the position of palettes and certain command settings are recorded in the Preferences file.

To ensure that tools and palettes are their standard settings, delete the preferences file before you begin each session.

To delete the Photoshop Preferences file for Adobe Photoshop 4.0 on the Macintosh:

1. Locate the Adobe Photoshop 4.0 Pres file in the Preferences folder in the System folder.

If you can't find the file choose Find from the desktop file menu, enter Adobe Photoshop 4.0 Prefs in the text box, and click find.

2. Drag the Adobe Photoshop 4.0 Prefs file to the Trash.
3. Choose Special, Empty Trash

To delete the Photoshop Preferences file for Adobe Photoshop 4.0 in Windows :

1. Click Start
2. Click Find
3. Click Files or Folders
4. Make sure Name & Location tab is selected
5. Click Browse next to Look in: drop-down list box
6. Select (C:), if you using computer labs at Cuyamaca College or your personal
7. Click Find Now
8. Locate and delete the file.

For Adobe Photoshop 5.0, "Adobe Photoshop Settings" folder or it's contents have to be deleted.

To do this on the Macintosh:

1. Locate the Adobe Photoshop Settings folder in the System folder.

If you can't find the file choose Find from the desktop file menu, and locate the folder.

2. Drag the Adobe Photoshop Settings folder or its contents to the Trash.
3. Choose Special, Empty Trash

To quickly locate and delete the above file or folder, create an alias (Macintosh) or shortcut (Windows) for the appropriate file or folder.

Preparing Images for Web Publication Using Adobe Photoshop

If you are going to use the scanner to import images into Adobe Photoshop, it is suggested to read "Introduction to Scanning" before starting scanning.

1. Start Photoshop.
   
   
2. Click on File menu and select Import, TWAIN or TWAIN_32 (whatever is available). Follow the scanning instructions, scan and open the scanned image in the Adobe Photoshop main window.
   If you are not scanning and want to open a saved image in the Photoshop then, select Open from the file menu. In the Open dialog box, locate the image and click Open.
   
   
3. Click on File menu, select Save As... and save the original image as a Photoshop image. Always keep a saved copy of the original image.
   
   
4. Click on Image menu on the menu bar and select Mode. In the Mode menu choose Indexed Color. (In this process the image will be converted to Indexed Color Mode i.e. 8-bit image.)
   
   
5. At this stage you may be asked, Flatten layers? Click on OK.
   
   
6. When the Indexed Color dialog box appears, set the parameters of the GIF image you want to create as follows:

• To save the image as a non-transparent GIF:
1. Click on File menu and select Save As
   
   
2. In the Save As dialog box, enter a name for your GIF picture in the File Name box and select CompuServe GIF (*.GIF) from the Save As drop down list box.
   
   
3. Click on Save button
   
   
4. In the GIF Options dialog box, check:
   
   
   • Interlace for gradual reveal of the picture on browser (larger file size and hence longer loading time on WWW), or
     
     
   • Normal for top to bottom reveal.
     
     

• To save the image as a transparent GIF:
1. Click on File menu, select Export and select GIF89a Export.
   
   
2. In the GIF Options dialog box, check:
   
   
   • Interlace for gradual reveal of the picture on browser (larger file size and hence longer loading time on WWW), or
     
     
   • Normal for top to bottom reveal.
     
     
3. In the GIF89a Export dialog box, select the hand tool to move and see the entire image in the preview window.
   
   
4. Click the eyedropper tool in the GIF89a Export dialog box. The eyedropper tool is used to select the colors you want to make transparent.
   
   
5. Drag the eyedropper tool over the Transparency From color menu and click the color(s) you want to make transparent.
   
   
6. Click OK.
   
   
7. In the GIF Export 89a dialog box enter the file name for the GIF picture and click on Save button.
   
   

Open your Web browser, locate and open the saved GIF Image to view.

Tip

One of the ways you can reduce the size of images for the Web publication is to turn off the Image Preview option in the Preferences dialog box. Turning off the Image Preview option saves files without a preview icon. To do this:

1. Choose File > Preferences > Saving Files.
   
   
2. Choose Never Save from the Image Previews menu.
   
   
3. Click OK.

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Preparing Images for Web Publication Using Adobe Photoshop

JPEG Format

If you are going to use the scanner to import images into Adobe Photoshop, it is suggested to read "Introduction to Scanning" before starting scanning.

1. Start Photoshop.
   
   
2. Click on File menu and select Import, TWAIN or TWAIN_32 (whatever is available.) Follow the scanning instructions, scan and open the scanned image in the Adobe Photoshop main window.
   
   

   If you are not scanning and want to open a saved image in the Photoshop then, select Open from the file menu. In the Open dialog box, locate the image and click Open.

3. Click on File menu, select Save As and save the original image as a Photoshop image. Always keep a saved copy of the original image.
   
   
4. To make sure that the image is in RBG Mode, click on Image menu and select Mode. If RBG Color is not selected, click to select it.
   
   
5. To flatten the image, click on Layer and select Flatten Image.
   
   
6. Once the image becomes flattened it is ready to be saved in JPEG format. Click on File menu and select Save As.
   
   
7. In the Save As dialog box, enter a name for your JPEG image in the File Name box, select JPEG from the Save As drop down list box and click Save button.
   
   
8. In the JPEG Option dialog box:
   
   • Enter a number between 0 and 10 for Image Options Quality: or choose from the four drop-down menu options. Or move the slider, left or right to choose the quality options.(They all perform the same function.)
     A Maximum setting will compress the image the least, and preserve image quality the most, but the resulting file size from this setting will be larger than with any other setting. In general, the compression level is on a scale of 1 to 10 where 1 being a very small file size, but low quality and 10 being very large file size, but high quality. Try different settings on different versions of the original image, and experiment the differences for a final decision.

   • In the Format Options menu click the Baseline (Standard) button to minimize the amount of data loss during compression (the most common format used in JPEG creation.) Or, choose Baseline Optimized to optimize image quality during compression.
     To produce a progressive JPEG file, choose Progressive for Format Option. This type of file will display in the Web browser in several passes, with more detail revealed with each pass. Choose the desired number of passes (scans) from the Scans drop-down menu.

9. Click OK or press Enter to create the JPEG image.
   
   

Open your Web browser, locate and open the saved JPEG Images to view.

 

Tip

One of the ways you can reduce the size of images for the Web publication is to turn off the Image Preview option in the Preferences dialog box. Turning off the Image Preview option saves files without a preview icon. To do this:

1. Choose File > Preferences > Saving Files.
   
   
2. Choose Never Save from the Image Previews menu.
   
   
3. Click OK.

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Preparing Images for Web Publication Using

Microsoft Photo Editor

It is suggested to read "Introduction to Scanning" before starting scanning images for Web publications. I assume that you are using the scanner in order to import images into the MS Photo Editor.

1. Put the original image on the scanner.
   
   
2. From the Desktop, click on the Start button.
   
   
3. Select Programs.
   
   
4. Select Microsoft Office
   
   
5. Click on Microsoft Photo Editor. The main window of Microsoft Photo Editor opens.
   
   
6. Select Scan Image from the File menu.
   
   
7. Click Preview.
   
   
8. Open the Type pop-up menu and select the appropriate type that image should be scanned and processed:
   
   The Type pop-up menu provides image type selections. The image contains the following items of information:
   • Color content (Black and White or Color)
     
     
   • Color depth (16 grays and 256 grays for Black and White, and 16 colors, 256 colors, or Millions of Colors for Color images)
     
     
   • Scan style (Drawing, Halftone, or Photo)
     
     
   • Sub-styles (Spot Color or Detailed for Photos and Normal, Diffusion, Fine, Extra fine, Horizontal Line, and Vertical Line for Halftones)

     When an image Type is selected the above information is automatically set for final scanning. You can find the values for any of these items by opening the Custom Image Type dialog box and selecting the item.

     When Automatic Find is active, DeskScan II, which is the scanning software, will automatically select an image type for the image after it does a Preview Scan. Automatic Find is activated by a check box in the Preferences dialog box under the Edit menu. If you want to edit the image manually, use the Help menu.

     Once you have completed this stage you are ready for final scanning and saving the image.

9. Click Final.
   
   The Final button and the Save and Save As commands in the File menu are nearly equivalent. The difference is that the Save command automatically saves the image to the last file name entered.

   Usually, a selection area is created in the Preview Area prior to a Final Scan. If a Final Scan is done without a selection area, the entire scanner copyboard is scanned and saved.

   To Save the Image File

   1. Select the file format, from Save as type: in the Save As dialog box. Select Compuserve GIF or JPEG, depending on your decision.
      
      
   2. Type the file name.
      
      
   3. Click Save.

Keep the image in the same place on the scanner copyboard during the scanning process to ensure a good scan. Final Scan does not re-paint the image to the screen. Instead, the Preview Scan or Zoom Scan image remains in the Preview Area.

If you are not scanning and want to open a saved image in the Microsoft Photo Editor then, select Open from the file menu. In the Open dialog box, locate the image and click Open. Select Save As from File menu and save the image in the required (GIF or JPEG) format.

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