# 5014- Using Scanners With CorelDRAW 5 A scanner is a device that translates a picture into an array of dots. The size of the dots is controlled by the scanning resolution, which can be modified from a very large dot to a very small dot, thus capturing the desired amount of detail from the image. This information is stored in a file as a bitmap or Raster image. As this results in a two dimensional image, height or depth is not a consideration in a conventional bitmap. There are two applications that can scan images within the CorelDRAW 5 Suite, they are Corel PHOTO-PAINT and CorelTRACE . Both of these programs use the TWAIN scanner interface to scan with TWAIN compliant scanner drivers. TWAIN is an interface that directly acquires image data from external sources (scanners) from within an application already running. This interface was designed to act as an industry standard making it possible for software companies to develop one version of software that can essentially be used with other TWAIN compliant applications. This new technology allows your system to store a smaller set of drivers which can be accessed by all TWAIN compliant applications. If you are experiencing difficulties getting the scanner to work with Corel Applications, refer to the Troubleshooting Section later in this document. Scanning Tips Images containing intensity values of either extreme of 0 or 255 may cause a loss of detail on the printed page. This value can be monitored using the Eyedropper Tool. Scanning an image at 1200 DPI will cause print times and the file size to increase exponentially, while in some cases, not affecting the quality of your job. This is especially true when your image is going to be printed at a smaller size. To estimate the size of a file to be scanned, use the following equation: (length in inches x DPI) X (width in inches x DPI) X (the number of color planes in the image) Note: Grayscale images have 1 color plane, RGB images contain 3 color planes and CMYK images use 4 color planes. Table 1. Approximate values of uncompressed bitmap file sizes based on the size of the image color depth and the DPI value used. It is best to scan at true scanner resolutions, those that do not use interpolation, when possible. When scanning at 263 DPI the scanner resizes the image internally before sending the data to the computer, depending on the algorithm used within the scanner, this may cause undesirable effects or results. Before converting an image to CMYK format in PHOTO-PAINT using the Image, Convert To Option, be sure that the job will be printed on a printer correctly selected in the Color Manager. Using an incorrect printer color profile can cause color shifts on the final output pages. For more information regarding Color Management the CorelDRAW manual. DPI And LPI DPI stands for Dots Per Inch and is simply a measure of a file's resolution. DPI measures how many dots exist along one axis within a single inch of the file. When printing or separating images, some devices specify LPI to be used to recreate the images on the printed page using a technique called Halftones. In the past, Laser Printers and Offset Printing Presses could print only two tones of any color, solid, where all of the ink is laid down in one spot and no ink coverage at all. This process is referred to as Black and White printing and was useful when newsletters, newspapers and books were the only things being printed. Its largest limitation, being unable to accurately reproduce photographs, was quickly surpassed by using Halftones. Halftones are the result of the output device creating a small grid made of device pixels and grouping together to treat them as one. These grids will be used to create tiny halftone dots that will simulate shades of gray throughout the image. By using halftones the human eye is "tricked" into thinking that they are looking at shades of colors when they are actually looking at a fine pattern of white and black dots. For more information regarding Halftones request Document #5013 from the Corel FaxBack System. In order to use Bitmaps at the optimum size for your layout, use the following equation to make a connection between scan resolution and output resolution by converting LPI to DPI: DPI=LPI X 2 Note: This equation can vary from 1.2 to 2 as some layout restrictions and scan limitations may make it impossible to use LPI X 2. For example, when scanning a 4.5" picture, import the image, do not modify its size on the printed page. The scanning resolution and output resolution will have a direct connection, if the image is scanned at 300 dpi, the optimum line screen would be 150 LPI. When the image being scanned is not the same dimensions as the desired output, use the information provided below to determine the correct scanning resolution: 1. To change LPI, the line screen that the page will eventually be printed with, to DPI, multiply LPI X 2. i.e. 150 LPI X 2 = 300 DPI of the printed page 2. Establish what size the image will be, in inches, on the printed page. 3. Calculate the total number of scan pixels required to adequately represent the bitmap. Optimum bitmap size (in Pixels) = DPI (LPI of final printed page X 2) X Longest dimension of image in the layout 4. Either scan, import, or resize the file so that it will closely match the desired size that you obtained from the formula in step 3. This is easy when importing images as the import filters in the Corel 5 Suite now allows you to resample and crop bitmaps when importing, whereas scanning may pose more of a problem. Most scanning modules allow the page layout values to be entered, allowing the scanner driver to calculate the proper resolution. If your scanner driver does not allow you to enter layout values, use the following formula to determine the correct scanning resolution: (DPI of scan) X (# inches across the longest side of the image) Example: If the original image size is 2.25" X 2.25" and the desired printed image is to be 4" X 4" at 150 lpi, the calculation of the required image size for the layout is: (150 lpi X 2) X 4" = 1200 pixels 1200 pixels / 2.25" (the original image size) = 533 dpi Therefore 533 dpi is the ideal value to use for scanning. As previously mentioned, it is best to use 'true' scanner resolutions making it best to scan this example image at 600 dpi. We also have the option to use lpi X 1.2, as stated above, in this case the scanner resolution recommended would be 300 dpi. General Notes And Troubleshooting Your Scanner When installing either Corel PHOTO-PAINT or CorelTRACE, you have the option to install a scanner at the original time of install or at a later time. To install at a later date, run the install again, click Custom Installation, and Some from the Corel PHOTO-PAINT options and then select the scanner driver that you wish to use. Corel provides some scanner drivers for a few scanners available on the market but any TWAIN compatible scanner should work within applications that support TWAIN, as long as the correct scanner driver is being used. When trying to select a scanner from the Select Source dialog box no scanners are listed, check in the WINDOWS\TWAIN directory to find the Data Source file (*.ds). If there is not a Data Source file under this directory, then the installation procedure was not complete and should be run again. If none of the buttons are functioning in the Image Source dialog box, the image source is looking for a scanner driver loaded in memory and cannot find one. If you are using the Corel Image Source, please refer to the driver chart below to verify that all of the required drivers are loaded in memory. If using another Image Source, contact the manufacturer for more information on the required scanner drivers. If the scanner still fails to operate please refer to the comments section in the driver chart below for special instructions. If there are no comments entered for the scanner or you would like further information, refer to the Troubleshooting Section of the online Help under Diagnosing General Mode Protection Faults or contact your scanner manufacturer.