Merge RGB Images
The Merge RGB Images command creates an RGB
color image by merging 3 separate images interpreted as the red,
green, and blue channel data. The source images are taken from an
Image Set opened in the source Image Window. The new
RGB image is opened in a new
Image Window.
The merging process uses parameters adjusted in a
docking pane attached to the
Image Window. This process is essentially a matter of
choosing the black level and white level for each of the channel
images, hence the docking pane includes several controls for
setting these levels for the component images. The picture below
shows the Merge RGB pane opened for a window containing
several of the sample images. Also see the example near the bottom
of the page.
Overview
The strategy behind this command is to adjust the
minimum pixel value and maximum pixel value for the channel images.
For merging the channel images, these values correspond to the
values that will become the black and "white" (or maximum color)
levels, respectively. Setting the minimum and maximum pixel values
effectively changes the contrast and brightness of each channel in
the merged LRGB image.
The values in the text fields are used for merging,
regardless of how they are set. Beyond simply typing a number into
each text field, several controls are provided for setting these
values.
The following table shows several ways to adjust
the minimum and maximum pixel values for the R channel image. These
same controls are provided for all three channels.
Controls for Setting Merge Values for the Red
Channel Image
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Select the source image from the image set.
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Automatically set the trackbar limits using
minimum and maximum pixel values from the image histogram.
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Minimum Value
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Shows the minimum value for merging. It may be
entered by typing.
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Calculate the minimum value (black limit) from
statistics inside the
Image Cursor. This sets the limits for the
trackbar.
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Adjust the minimum value using the trackbar
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Maximum Value
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Shows the minimum value for merging. It may be
entered by typing.
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Calculate the maximum value (white limit) from
statistics inside the
Image Cursor. This sets the limits for the
trackbar.
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Adjust the maximum value using the trackbar
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The [Merge] button
scales each of the images using minimum and maximum values from the
text fields. The Auto Merge check box
enables automatic merging after changing any of the six trackbars.
When the channels are merged, Mira creates the new RGB image in a
new
Image Window. If the images are merged again, the new
RGB image overwrites the previous RGB image in the window. The
final color brightness, contrast, and color balance of the RGB
image can be refined using the
Palette Properties dialog for the output window.
The [Save] and
[Reset] buttons save and re-load the
parameters below the horizontal line.
Procedure for Merging Images
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Open the images to be used for the R, G, and B
channels as an
Image Set in an
Image Window. Make sure this source window is on
top.
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From the Image Window's Process > RGB
Images menu, click Merge RGB Images
to open the docking pane into the source window.
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Select the output type as 24-bit or 48-bit.
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Select channel images from the image set using
the R, G, and B channel drop lists.
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Adjust the Min
Value and Max Value for each
channel using the controls in the docking pane.
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Click [Merge] to
combine the channel images. The RGB image will open in a new
Image Window.
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Tip: The
Auto Merge checkbox
causes the channel images to be re-merged immediately after
adjusting the trackbar or pressing Enter for a text field.
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If the brightness, contrast, or color balance
need to be changed, repeat steps 5 through 7. Repeat steps 4
through 7 if you need to select different channel images.
Example: Showing Object Motion
RGB Merging is useful for data visualization tasks
beyond simply creating a color image from filtered monochrome
images. This example illustrates how motion of Comet Hyakutake
(Comet C/1996 B2) may be quickly visualized by merging 3 exposures
acquired at different times. After loading the Hyakutake sample
images provided with the Mira installation (see the
Image Window above), the first, middle, and last
images were selected as the R, G, and B channels. The names of
these files represent a time sequence, so images 120, 135, and 145
were chosen to mark the beginning, middle, and end of the exposure
sequence. Mira calculates the default black and white levels when
an image is selected, so no other adjustments were made. In the
merged RGB image below, notice how the first (red) image shows the
beginning position while the last (blue) image shows the final
position of motion relative to the stars. Note that the color of
the R and B channel images is shifted toward green by the
overlapping middle image used for the G channel.
Related Topics
Working with RGB Images
Merge LRGB Images
Extract Channel
Mira Pro x64 8.71 User's Guide, Copyright Ⓒ 2024 Mirametrics, Inc.
All Rights Reserved.
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