Difference between revisions of "Changing Image Contrast"
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<div style="font-style: normal; font-weight: normal; margin-bottom: 6pt; 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"> <span style="font-style: normal; font-weight: normal; text-decoration: none; text-transform: none; vertical-align: baseline"><font color="#0000ff">[[Image:InvertLUTIco.jpg]] </font></span> The invert LUT icon creates a negative of an image. <br /></font></div><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 create a negative 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 Select the image window of the image you want to invert.<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 Click Invert LUT.<br /></font></div> | <div style="font-style: normal; font-weight: normal; margin-bottom: 6pt; 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"> <span style="font-style: normal; font-weight: normal; text-decoration: none; text-transform: none; vertical-align: baseline"><font color="#0000ff">[[Image:InvertLUTIco.jpg]] </font></span> The invert LUT icon creates a negative of an image. <br /></font></div><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 create a negative 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 Select the image window of the image you want to invert.<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 Click Invert LUT.<br /></font></div> | ||
− | Based on the 256-step color values scale, MIPAV assigns the inverse value to each pixel of the image (refer to | + | Based on the 256-step color values scale, MIPAV assigns the inverse value to each pixel of the image (refer to Figure 27). |
<div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 0pt; margin-right: 0pt; margin-top: 5pt; text-align: left; text-decoration: none; text-indent: 0pt; text-transform: none; vertical-align: baseline"><font color="#000000"> <span style="font-style: normal; text-decoration: none; text-transform: none; vertical-align: baseline">'''<font color="#000000">Tips:</font>'''</span> You may wish to apply a LUT to the image or adjust the histogram of the image first before applying creating the negative.The Invert LUT icon is a toggle. To change the image back to its previous appearance, simply select Invert LUT again. To change the image back to its <span style="font-weight: normal; text-decoration: none; text-transform: none; vertical-align: baseline">''<font color="#000000">original</font>''</span> appearance, select Reset LUT.<br /></font></div><div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 0pt; margin-right: 0pt; margin-top: 5pt; text-align: left; text-decoration: none; text-indent: 0pt; text-transform: none; vertical-align: baseline"><font color="#000000"> <span style="font-style: normal; text-decoration: none; text-transform: none; vertical-align: baseline">'''<font color="#000000">Note:</font>'''</span> Invert LUT appears on two different windows: in the Image toolbar in the MIPAV window (select Toolbars > Image toolbar to display the toolbar) and in the LUT toolbar in the Lookup Table window. <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"> | <div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 0pt; margin-right: 0pt; margin-top: 5pt; text-align: left; text-decoration: none; text-indent: 0pt; text-transform: none; vertical-align: baseline"><font color="#000000"> <span style="font-style: normal; text-decoration: none; text-transform: none; vertical-align: baseline">'''<font color="#000000">Tips:</font>'''</span> You may wish to apply a LUT to the image or adjust the histogram of the image first before applying creating the negative.The Invert LUT icon is a toggle. To change the image back to its previous appearance, simply select Invert LUT again. To change the image back to its <span style="font-weight: normal; text-decoration: none; text-transform: none; vertical-align: baseline">''<font color="#000000">original</font>''</span> appearance, select Reset LUT.<br /></font></div><div style="font-style: normal; font-weight: normal; margin-bottom: 0pt; margin-left: 0pt; margin-right: 0pt; margin-top: 5pt; text-align: left; text-decoration: none; text-indent: 0pt; text-transform: none; vertical-align: baseline"><font color="#000000"> <span style="font-style: normal; text-decoration: none; text-transform: none; vertical-align: baseline">'''<font color="#000000">Note:</font>'''</span> Invert LUT appears on two different windows: in the Image toolbar in the MIPAV window (select Toolbars > Image toolbar to display the toolbar) and in the LUT toolbar in the Lookup Table window. <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"> | ||
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|+ <div style="font-style: normal; margin-bottom: 3pt; margin-left: 0pt; margin-right: 0pt; margin-top: 9pt; text-align: left; text-decoration: none; text-indent: 0pt; text-transform: none; vertical-align: baseline">'''<font color="#000000"> Figure 27. Image before and after inversion<br /></font>'''</div> | |+ <div style="font-style: normal; margin-bottom: 3pt; margin-left: 0pt; margin-right: 0pt; margin-top: 9pt; text-align: left; text-decoration: none; text-indent: 0pt; text-transform: none; vertical-align: baseline">'''<font color="#000000"> Figure 27. Image before and after inversion<br /></font>'''</div> | ||
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− | | | + | |[[Image:exampleImageBeforeandAfterInversion.jpg]] |
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− | [[Image:exampleImageBeforeandAfterInversion.jpg]] | + | |
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== Comparing images using alphablending == | == Comparing images using alphablending == |
Revision as of 15:50, 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.
Lookup Table dialog box
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 Figure 27).
Comparing images using alphablending
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