Image Enhancement
You may want to enhance your images prior to
scanning them. MagicScan provides some beneficial features for you to use
to modify scanned images. Some of these featrues include setting highlight
and shadow values for your image, adjusting the image curve, neutralizing
your image, inverting your image, changing the color balance for your image,
and so forth.
Image Enhancement consists of several functions.These functions have been placed together in a tabbed dialog box. To access one of these functions, just click on the protruding tab at the top of the dialog to bring it to the front. At the top of each dialog box there are thumbnail representations of the original and enhanced images ("Sample 1& 2"). You can see the effects of changes to a previewed image through the "Sample" thumbnails without committing yourself to full image processing. Original is the thumbnail view for the previewed image and "Sample 1 & 2" are the thumbnail views for the images after they have been enhanced. "Sample 1 & 2" give you a means of comparing two enhanced images. Click on the desired Sample to choose the required image and click the "OK" button to finalize the selection. Each function is explained below. Simply click on the topic that you would like to learn more about. The corresponding information will be displayed and will show you what effect it will have on your images. |
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The Level Adjustment dialog box shows the distribution of brightness levels in your image. To adjust the histogram plot, drag the triangular handles, located below the horizontal bar, to desired values. The left (black) handle controls changes to the shadow levels. The right (white) handle controls changes to the highlight levels. The middle (gray) handle controls changes to the midtone levels.
By varying the Shadow points and Highlight points you can change the relative shades and highlights of the image. The Shadow point represents the darkest value and the Highlight point is the brightest value. The Midtone point represents the gamma setting for your particular screen. On the histogram, the Shadow and Highlight scales are divided into 255 units.
Therefore, all pixels in the original that are darker than the current shadow point are now completely black in the enhanced image. Conversely, all pixels in the original that are brighter than the current highlight point are now completely white in the processed image.
Setting the highlight point to 200 renders all pixels greater than or equal to 200, on the original, completely white in the processed image. Similarly setting the Shadow point to 200 renders all points less than or equal to 200, on the original, completely black in the enhanced image.
The Midtone is a relative measure of the gamma of your monitor. The scale for Midtone ranges from 0 to 255. The gamma curve is on a geometric series. That means at a value of 255 it tends to infinity. The Midtone is bound by the Shadow and Highlight terms and cannot exceed them at any time. So, a gamma of 1 is equivalent to a Midtone of 128 providing the Shadow is set to 0 and the Highlight is set to 255. Similarly, if the Shadow is set at 20 (lower bound) and the Highlight is set at 220 (upper bound), a gamma of 1 is equivalent to a Midtone of 120.
You can restrict the effect of the Histogram plot changes to a single color by selecting either the Red (R), Green (G), or Blue (B) channel buttons. Or you may select the Master channel to apply the Histogram to all three channels.
Note: If you are using a Grayscale image type, the RGB readings do not appear in the dialog box.
Operation:
Original | Sample 1 | Sample 2 |
Select the Tonal Map tab from the Enhancement tabbed dialog box
The Tonal Map is yet another way to adjust highlight, midtone, or shadow levels in your images. When you open the Tonal Map dialog box, a tonal map consisting of a diagonally straight line appears. Notice that at every point on the default tonal map, the output shadow, midtone, and highlight brightness levels are equal to the input shadow, midtone, and highlight brightness levels.
The shape and slant of the tonal map represent brightness level ratios between the input of the original image and the output image data. By clicking on the tonal map line, a "hand"-shaped cursor will appear which can be dragged in such a way as to alter the shape of the tonal map line. The horizontal axis represents the original input brightness and the vertical axis represents the enhanced brightness. Values on either scale range from 0 to 255.
If you deform the curve into a convex shape above the original diagonal,
the enhanced image will be brighter than the original.
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There may be occasions when the scanned image is tinted with an undesirable hue. In order to rectify this problem, click the Neutralization button, which invokes a color adjustment wheel (similar to Color Adjustment color wheel).
Operation:
This option allows you to control the distribution of color by means of saturation or dilution of a particular color.
The dialog box displays a continuous color spectrum on a wheel. By clicking on certain areas of the wheel, "Sample 1" changes to a particular hue which governs the distribution.
Operation:
This option allows you to change the mixture of colors in a color image. You can use this option to emphasize certain colors or to diminish unwanted ones.
Selection of the Shadow, Highlight, or Midtone check boxes in the dialog box let you focus the color balance changes on three different brightness levels. The three triangular sliders on the color bars allow you to adjust the color balance in one or more of the 3 color (RGB) channels.
Operation:
This function inverts all the tone values such that each color in the
original is exchanged with its color complement. This effect is similar
to using the Tonal Map to tonally invert the image.
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