Combine Image & Mosaic - Basic Steps to Apply a Filter with Blend Mode, Opacity, & Image Mask

Combine Image & Mosaic can be used to apply a stretch, smooth, sharpen, deconvolution, or color adjustment filter with optional blend mode, opacity, and mask to color or monochrome images. The advantage of using Combine Image & Mosaic to apply a filter is direct modification of the filter image and its mask.


This tutorial explains how to use Multiresolution (wavelets) to sharpen an image. A Micro Curve adjusted luminance mask is created and used to apply the sharpening filter to just the highlights and stars. Opacity is used to blend the sharpened image with the initial image to soften the composite image. Similar steps can be used to apply any filter or mask. Multiple masked filters can be applied.


Initial narrow band image of NGC 6888.








Step 1) Open the Combine Image & Mosaic Tool and Assign the Initial Image


Select Special Functions | Mosaic Setup from the ImagesPlus main menu. Enter a name for the composite image then press OK. The Combine Image & Mosaic tool is displayed and a new composite image is created. The composite is black since no image layers have been added yet.



Check the Add Image box on the Combine Image & Mosaic tool then left click on the initial image. The initial image is added as the first image layer in the layer tree and is displayed in the composite image window.





Step 2) Duplicate the Initial Image and Assign to Image Layer 2


Left-click on the initial image or press the Image button on Combine Image & Mosaic to make the initial image the active image. Use the Duplicate (...) toolbar button to duplicate the initial image. Duplicate image shown top left.



Check the Add Image button on Combine Image & Mosaic then left click on the duplicate image. The duplicate image is added as the second or top image layer in the layer tree.





Step 3) Create a Mask for Image Layer 2


A luminance mask created from the image to be sharpened works well since sharpening is applied to the image only at brighter areas of the mask. Left click on the top layer image window or press the Image button on Combine Image & Mosaic with the top layer active to make the image active. Now use the Luminance Mask toolbar button (2nd from top on left vertical toolbar) to create a mask.



Left click on the top image layer in the tree to make it the active layer if it is not already the active layer marked with an arrow (->). Check the Add Mask button on Combine Image & Mosaic then left click on the mask image window. The mask is assigned to the top image layer.






Step 4) Image Window Management


The Combine Image & Mosaic tool can be used to manage the display of the composite image and all image layers and their masks. The Open Images | Stack option can be used to move all images to the upper left corner of the computer screen and place them on top of each other. Use the Combination button on Combine Image & Mosaic to display and active the composite image window. Select an image layer in the layer tree of Combine Image & Mosaic then press the Image or Mask button to display and active the image or mask window. Each image layer and mask can have its own unique Process History layered filter list.








Step 5) Sharpen Top Image Layer


Select the top layer in the image layer tree on Combine Image & Mosaic then press the Image button to display and active the top layer image window. Move the Finest and Fine sliders of Multiresolution (wavelets) to the right to sharpen the top image layer window. The Min Apply, Max Apply, and Feather Range sliders on Multiresolution could be used to restrict sharpening to just the background, midtones, or highlights in addition to the mask.








Step 6) Check Composite Image


On Combine Image & Mosaic press the Combination button to display the composite image then press the Apply button to update the composite image using the mask sharpened top image layer. Opacity of the top image layer is reduced to 0.476 to blend the mask sharpened top image layer with the initial image. With the top image layer active in the tree check and uncheck the Use Image or Use Mask options to alternate between sharpened and initial image. Normal blend mode is set on the top image layer so that only opacity blending is used to mix with the initial image.








Step 7) Modify Mask


With the top image layer active in the tree press the Mask button on Combine Image & Mosaic to dispaly the mask image window. Apply Stretch | Micro Curve to increase the brightness of the mask. Brighter mask areas will apply more sharpening to the top image layer window than darker mask areas.








Step 8) Check Composite Image


On Combine Image & Mosaic press the Combination button to display the composite image then press the Apply button to update the composite image using the micro curve adjusted mask. Opacity of the top image layer is increased to 0.893 to blend the mask sharpened top image layer with the initial image. With the top image layer active in the tree check and uncheck the Use Image or Use Mask options to alternate between sharpened and initial image. Press the Flatten button to release the composite image for further processing.



Initial NGC 6888 image before multiresolution (wavelet) sharpening with luminance mask.



NGC 6888 image after multiresolution (wavelet) sharpening with Micro Curve adjusted luminance mask.




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