Image Combining Methods
Mira provides many mathematical choices for combining a set of images. This command produces a final image in which the pixel at each coordinate is a mathematical combination of the pixels at the same coordinate in all of the source images.
In considering the combining methods described below, keep in mind that each method works by processing all the values at each (column,row) location in turn. At each point, the value is drawn from each image and combined using the selected method to create 1 output pixel. This is repeated for each point until the entire image is processed.
These methods vary from simple linear pixel merging methods to non-linear weighted averaging methods. Use them to Combine Image Set into a single, higher image having higher signal-to-noise ratio.
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Mean |
Creates an image containing the arithmetic mean value over all images at each point. The Mean method combines the pixels as a straight average with no weighting or rejection of bad values. This is the preferred method if the images can be considered to contain only well-behaved statistical noise. |
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Mean with Zero Mask |
Creates an image containing the mean value of pixels from all images except those with a value of 0, which are interpreted as "don't use". Pixels with a value of zero are not included in calculating the mean value. See the Register Images command for an application of this method. |
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Median |
Creates an image containing the median values of all images at each point. This method has good ability to reject extreme values. For a given number of input images, the noise in the resulting image is not as low as that which can result from Mean combining methods. |
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Sum of Values |
Creates an image containing the sum of the values from all images at each point. If using this method, be sure the output pixel type has greater sufficient numeric range to handle the resulting values. For example, combining 100 16-bit images having peak luminance of 50,000 may result in some output pixels being as high as 5,000,000. Clearly 5,000,000 is not within the 0-65535 range of a 16 bit unsigned integer image. To handle this change the output pixel type to 32 bit integer or 32 bit real. |
Combine Image Set, Combine Files, Register Images, Image Region Statistics