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.
The Merge RGB Images command opens from the Image Window > Process > RGB Images menu.
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.
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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 |
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.
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.
From the Image Window's Process > RGB Images menu, click Merge RGB Images to open the docking pane into the source window.
Select the output type as 24-bit or 48-bit.
Select channel images from the image set using the R, G, and B channel drop lists.
Adjust the Min Value and Max Value for each channel using the controls in the docking pane.
Click [Merge] to combine the channel images. The RGB image will open in a new Image Window.
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.
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.
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.
Mira Pro x64 8.72 User's Guide, Copyright Ⓒ 2024 Mirametrics, Inc.
All Rights Reserved.
