MegaStack™ Image Stacker is a plug-in that extends the image stacking features of Chasys Draw IES to support stack sizes that are too large to load into the workspace of Chasys Draw IES. MegaStack™ works with the files directly on disk instead of RAM, thus eliminating stack size limitations – there is no upper limit on the number of files you can stack when you use the plug-in. Such unlimited stacking is very important in astrophotography scenarios, where large stacks involving hundreds or even thousands of frames are not uncommon.
To speed things up, MegaStack™ processes images in parallel when it detects a multi-core CPU, multiple CPUs or hyperthreading.
How do I use MegaStack™ Image Stacker?
From the user’s perspective, MegaStack™ Image Stacker works just like the standard Image Averaging Stacking feature. The difference lies in the fact that it has no limitations and indeed has some extra features that the standard stacker doesn’t have, such as the use of dark-frames.
To use the MegaStack™ Image Stacker, go to the File menu and select Import from Device. You'll be presented with a dialog box where you can choose the device plug-in you want to import an image from. Select "WIA Imaging Support" and then click "RECEIVE".
This is the GUI for aligning the images:
The first layer is used as the reference, and always has the offsets (0,0). All other layers are aligned against this layer, with offsets specified in pixels. MegaStack™ Image Stacker can align the images for you based on reference points that you provide; you can also align the images manually. The following functions are supported:
Function
Description
Offsets
This command tells Chasys Draw IES to attempt to calculating the offsets of all layers automatically using its image registration algorithm. It uses the reference marked by the crosshairs. You are advised to double-check the results and use the refine option or make manual adjustments since the algorithm may make mistakes. Chasys Draw IES will use the selected reference point to do the calculation.
Rotation
This command tells Chasys Draw IES to attempt to calculating the rotations of all layers automatically using its image registration algorithm. It uses two references; the reference marked by the crosshairs for the center of rotation and the reference marked by the diagonal crosshairs for the actual rotation. You are advised to double-check the results and use the refine option or make manual adjustments since the algorithm may make mistakes. Chasys Draw IES will use the selected reference point to do the calculation.
Reset
This command sets all offsets to (0,0).
Import
This command copies the current layer positions in the workspace and uses them as layer offsets. This may be useful where images have already been aligned in an image editor that aligns images using offsets of layers.
Refine
This command tells Chasys Draw IES to attempt to recalculate and refine the offset or rotation of the current layer automatically using its image registration algorithm. It uses the current offset or rotation as a reference point for the calculation. Chasys Draw IES will use the selected reference point to do the calculation.
For comparing the images, several functions are provided under “Display”. The default is “DevRoot”, which highlights the differences between the layer being aligned and the reference layer (the first layer).
This is the GUI for averaging the images:
The sliders for sharpening and gamma operate on the high-precision summation data to minimize rounding errors. The “outliers” settings determine how many pixels can be treated as outliers caused by noise or other defects and thus omitted from dynamic range calculations. Ten outliers per mega-pixel is usually a good rule of thumb. The cut-off points determine the portion of the range to use; the default is to use the entire range (0% – 100%).
