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Scanning Software for BeOS

Manual Version 1.0b3

Quick Start

If you're unsure where to start, but Skeeter has successfully started up, click on the Preview button to see what is on your scanner bed.

If you haven't already taken a look at the At-a-glance page, start there because it has almost all the information you need if you're familiar with scanners and have used other scanning software utilities before.

Scan Process

Here is the general process for scanning with Skeeter:

Controls

This section is a description of the parts of Skeeter you can interact with to get the scanned image you want.

Image Type

Skeeter supports three different image types, selectable by this group of radio buttons. With its live preview feature what it actually does is scan in color, then reduce the information to gray and then thresholded binary data when required for display. This way you can change the image type without re-previewing.

If your scanner does not support one of the image types, the corresponding button will be disabled.

Resolution

The resolution setting affects the final scanned output, which is either saved to a file or, if an application has invoked Skeeter via the ScannerBe API, transferred directly to the application. It is always measured in dots-per-inch, or, more accurately, pixels-per-inch. The TIFF file format, which Skeeter supports natively, supports specifying the resolution, though the Datatypes file formats do not. Keep the destination of your image in mind when deciding which file format to use, as it may rely on resolution information.

If you try to type in a value which is bigger or smaller than the maximum or minimum values allowed by the scanner, respectively, it will be adjusted to those limits.

Of course, the resolution of the data shown in the preview area is unknown to you, because it may vary with the size of the preview area or how far in you have zoomed.

Scaling

The scaling setting affects the final scanned output. It's how you "blow-up" or "shrink" your selected image so it is a certain size. For example, if you select just a logo from a business card to scan, it might only be a half-inch square. But if you want to print it out so it filled part of a letter size page, you would need to adjust the scaling until the size indicator showed you the size you wanted. You can select the units which are shown on the size indicator in the General Settings window.

The minimum and maximum scaling values shown at the top and bottom of the slider are values returned by the scanner and are affected by things like the scanner's optical resolution, and any the firmware algorithms used to give a higher interpolated resolution. Typically, changing the resolution also changes the minimum and maximum scaling values since scanner vendors try to optimize the tradeoff between resolution and scaling ability.

If you manually enter a scaling value, you must either type Enter or tab to the next text-entry field before the setting takes effect.

Brightness and Contrast

These two controls are the primary way you adjust the image appearance. The brightness control, indicated by the circle with light-rays coming out of it, adjusts how bright or dark the image appears. Increasing it will make the image brighter, decreasing it will make the image darker. The contrast control, indicated by the half-white/half-dark circle, adjusts the difference between the darkest and lightest tones in the image. Increasing it will make more of the tonal range read by the scanner appear black or white, while decreasing it will make more of the tonal range fit within a smaller range of brightness and darkness that you perceive.

More accurately, if you represent the transfer of the image as a straight line on a graph of brightness with the scanner measurements on the x-axis and the image you perceive on the y-axis, adjusting the brightness control changes the y-intercept of that line while adjusting the contrast control changes the slope of that line. The default settings of the controls in the middle of their ranges represents a 45-degree angle line (slope=1) from the bottom left corner to the top right corner (y-intercept=0).

The units shown in the indicators below the controls are somewhat arbitrary, and consists of whatever range the scanner returns. It is typically between 0 and 255, but this may vary depending on the particular scanner. You should think of the numbers simply as reference points which you can type in if you want to return to a particular set of values.

If you manually enter a value for brightness or contrast, you must either type Enter or tab to the next text-entry field before the setting takes effect.

Automatic Exposure

Since the average person usually has some difficulty setting the brightness and contrast controls quickly and to their liking (each control affects a different degree of freedom, each of which affects the entire tonal range), this button measures the image contained within the selection rectangle in the preview, and adjusts the brightness and contrast controls for the "best" appearance. In this case, "best" means the brightest and darkest parts of the image fill the entire range between black and white.

Of course, if it is not quite right, you are free to tweak the controls manually. The automatic exposure button is meant as a tool to get the right first-pass guess at how you want the image to look. Since it only takes measurements within the selection rectangle you have dragged in the preview area, you can move the selection area around the preview area kind of like a photographic spot meter, clicking the automatic exposure button and observing the settings when the selection rectangle is over a part of the image in which you are most interested.

It's always an interesting exercise to see the variation in illumination which occurs as the light bar moves down the scanner bed: put a white piece of paper on the scanner bed and preview it, then select the entire page in the preview area and click the automatic-exposure button.

This is the large area which occupies most of the main Skeeter window, and is where your previewed images appear. When you click on the Preview button, a scan is made and the resulting image data is displayed in the preview area. Not until you click the Scan button does the image actually get saved anywhere other than in the preview area.

When you drag a selection rectangle in the preview area, the Preview button is renamed to Zoom, which when clicked attempts to re-preview scan at a higher resolution, in order to fill the preview area with the portion of the image you have selected.

If the "Preview area drag and drop" is checked on in the General Settings window, then you may drag an image from the preview area to any application which supports the Dropped Image Format. You do this by dragging the selection rectangle from its middle (when the cursor switches to a hand) until the cursor goes outside of the preview area boundary. When this is done, the selection area turns from a dashed line to a gray line, and the drag is in progress.

Remove the selection area by clicking outside of it, in which case the image that will be scanned will be whatever shows in the preview area, and the image size indicator will reflect its size.

The Screen Calibration window lets you adjust your scanned images to match the particular behavior of your display screen. Each display is different, and generally has a response that is measured by a curve, and not a straight line which could be compensated for by the brightness and contrast controls.

This "gamma" curve can be measured by adjusting the slider in the Screen Calibration window until the three gray areas appear the same brightness. The two panels on the sides consist of alternating black and white lines, thus giving a 50% gray appearance, no matter what type of display you have. The panel in the middle is adjusted by the slider and consists of the display's real gray values. When they match, we have one data point on the gamma curve, which can then be extrapolated with some degree of accuracy.

Skeeter only uses one gamma value to adjust the scanned images, and the adjustment only takes effect if the check box in the Screen Calibration window is clicked on. In this case you will have "gamma corrected data"  in your scanned images. If it is checked off, you will have "linear data" in your scanned images. Some applications or drivers want one or the other, so it's up to you. If a calibration facility is ever incorporated into the BeOS, you will probably want to use linear data, or get an updated version of Skeeter which is compatible.

Skeeter supports TIFF natively, plus formats translated via the Datatypes library. The file format is selected from the save-file panel which appears when you click the Scan button.

Skeeter will scan from an automatic document feeder connected to your scanner. If you enter a name in the save window, and your ADF has more than one page in it, Skeeter will save multiple image files, each with a "-XX" suffix where XX is a number starting at 2 and increasing by one for each page. The only thing you have to be careful about is that a preview scan will feed a page, so you typically want to do a normal preview with a "test page" on the scanner bed to get the settings right, before you place your documents in the ADF.

Some user settings are maintained by Skeeter: window positions, the selected scanner add-on, etc., are saved using the libprefs library.