Difference between revisions of "Changing Image Contrast"
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[[Image:LUTIco.jpg]] To generate a histogram of an image, you can use the Lookup Table icon or call LUT > Histogram LUT. To obtain a histogram summary, which is in the tabular form, use the Algorithms > Histogram Tools > Histogram Summary command. | [[Image:LUTIco.jpg]] To generate a histogram of an image, you can use the Lookup Table icon or call LUT > Histogram LUT. To obtain a histogram summary, which is in the tabular form, use the Algorithms > Histogram Tools > Histogram Summary command. | ||
− | <div style="font-style: normal; margin-bottom: 6pt; margin-left: 0pt; margin-right: 0pt; margin-top: 14pt; text-align: left; text-decoration: none; text-indent: 0pt; text-transform: none; vertical-align: baseline">'''<font color="#000000"> To generate a histogram for an image<br /></font>'''</div><div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 18pt; margin-right: 0pt; margin-top: 6pt; text-align: left; text-decoration: none; text-indent: -18pt; text-transform: none; vertical-align: baseline"><font color="#000000"> 1 Open an image. The image appears in an image window.<br /></font></div><div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 18pt; margin-right: 0pt; margin-top: 6pt; text-align: left; text-decoration: none; text-indent: -18pt; text-transform: none; vertical-align: baseline"><font color="#000000"> 2 Do either of the following: click Lookup Table icon or select LUT > Histogram-LUT. For images that do not contain VOIs, the Lookup Table window opens. <br /></font></div><div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 18pt; margin-right: 0pt; margin-top: 6pt; text-align: left; text-decoration: none; text-indent: -18pt; text-transform: none; vertical-align: baseline"><font color="#000000"> 3 For images that contain VOIs, the Histogram dialog box appears. In the dialog box, select either Whole image or VOI region(s).<br /></font></div><div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 18pt; margin-right: 0pt; margin-top: 6pt; text-align: left; text-decoration: none; text-indent: -18pt; text-transform: none; vertical-align: baseline"><font color="#000000"> 4 Click OK. A progress message appears. After a few moments, the Lookup Table window ( | + | <div style="font-style: normal; margin-bottom: 6pt; margin-left: 0pt; margin-right: 0pt; margin-top: 14pt; text-align: left; text-decoration: none; text-indent: 0pt; text-transform: none; vertical-align: baseline">'''<font color="#000000"> To generate a histogram for an image<br /></font>'''</div><div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 18pt; margin-right: 0pt; margin-top: 6pt; text-align: left; text-decoration: none; text-indent: -18pt; text-transform: none; vertical-align: baseline"><font color="#000000"> 1 Open an image. The image appears in an image window.<br /></font></div><div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 18pt; margin-right: 0pt; margin-top: 6pt; text-align: left; text-decoration: none; text-indent: -18pt; text-transform: none; vertical-align: baseline"><font color="#000000"> 2 Do either of the following: click Lookup Table icon or select LUT > Histogram-LUT. For images that do not contain VOIs, the Lookup Table window opens. <br /></font></div><div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 18pt; margin-right: 0pt; margin-top: 6pt; text-align: left; text-decoration: none; text-indent: -18pt; text-transform: none; vertical-align: baseline"><font color="#000000"> 3 For images that contain VOIs, the Histogram dialog box appears. In the dialog box, select either Whole image or VOI region(s).<br /></font></div><div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 18pt; margin-right: 0pt; margin-top: 6pt; text-align: left; text-decoration: none; text-indent: -18pt; text-transform: none; vertical-align: baseline"><font color="#000000"> 4 Click OK. A progress message appears. After a few moments, the Lookup Table window (Figure 26) opens.<br /></font></div><div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 0pt; margin-right: 0pt; margin-top: 0pt; text-align: left; text-decoration: none; text-indent: 0pt; text-transform: none; vertical-align: baseline"><font color="#000000"> |
'''Figure 25. The Lookup Table window (A) and Histogram dialog box (B)'''<br /> | '''Figure 25. The Lookup Table window (A) and Histogram dialog box (B)'''<br /> | ||
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− | |[Image:LUTDialogBox.jpg]] | + | |[[Image:LUTDialogBox.jpg]] |
|[[Image:HIstogramDialogBox.jpg]] | |[[Image:HIstogramDialogBox.jpg]] | ||
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Revision as of 14:56, 9 February 2012
Contents
Using the right mouse button
The right mouse button provides you with a very simple way of changing image contrast. To do so, open an image and then hold down the right mouse button and drag it around the screen. The cursor changes from a red cross to one that is shown in Figure 23. To restore an image to its original appearance, refer to "Restoring images to their original appearance".
Figure 23. Changing image contrast using the right mouse button
When you drag the cursor up and down or across the image, the image may become darker and gradually disappear or become lighter in appearance. At some points you may be able to create a negative of the image.
Adjust Window and Level
The Adjust Window and Level icon on the Image toolbar provides another way to change the contrast of images.
Figure 24. The Level and Window dialog box
Move each slider up or down to change the contrast of the image. The changes are immediately effective in the image.
To adjust image contrast
Restoring images to their original appearance
In addition, you can click the Gray icon to restore the image to grayscale if you have changed it or added colors.
Improving contrast by generating and modifying histograms
To generate a histogram of an image, you can use the Lookup Table icon or call LUT > Histogram LUT. To obtain a histogram summary, which is in the tabular form, use the Algorithms > Histogram Tools > Histogram Summary command.
transfer function reflects the relationship between the original image intensity values and how they are mapped into the LUT. The line in the LUT represents the transfer function.
To change back to the original grayscale intensities, click Gray LUT in the MIPAV window.
Figure 26. Lookup Table dialog box
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Applying color to images using predefined LUTs
Using interpolation to smooth images
If you are zooming in on a portion of an image and want to reduce the appearance of pixilations in the image, make sure to select the Interpolate image check box. Interpolation smooths the pixilation. |
To change back to the original grayscale intensities, click Gray LUT in the MIPAV window.
Creating negatives of images
Based on the 256-step color values scale, MIPAV assigns the inverse value to each pixel of the image (refer to [MIPAV_QuickStart.html#1993908 Figure 27]).
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Comparing images using alphablending
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