Starguide - A Practical Guide to Astro-Photography

PixInsight - Image Post Processing

Resample and Resize

updated: 2021-05-23

Purpose

Changes the dimensions (and file size) of an image by interpolation of new pixel values from original pixel data. 

The Resample process is a basic geometric tool that allows resizing a target image using several pixel interpolation algorithms. As in the case of Crop, this tool allows the user to work either with absolute dimensions in pixels, centimeters or inches, or with relative dimensions. It also allows modifying the target image's resolution in pixels per inch or pixels per centimeter.

Unlike Crop and FastRotation, which only copy or exchange existing pixel values to different locations on the target image, Resample generates output pixel values by interpolation from source pixels. This is an important difference because pixel interpolation is a destructive operation, in the sense that it cannot be undone to recover the original data. With non-interpolating tools such as Crop and FastRotation, on the other hand, you could apply an unlimited number of operations and, as long as no pixels were cropped, the original pixel values wouldn't be modified.

Activation

Menu: Process 🡺 All Processes 🡺 Resample

Process Explorer: Geometry 🡺 Resample

Input

Corrected image, file name “*_i_c_DBE_BN_CC_HT.xisf” or similar into sub folder "aligned"

Output

Corrected image, file name “*_i_c_DBE_BN_CC_HT_RS.xisf” or similar into sub folder "aligned"

Previous Step

• Color Calibration

Next Step

• Background Improvement

Tutorial

https://www.youtube.com/watch?v=JtA4UoaAAas  (Part 6  DBE - starts around timestamp 2m56s)

Step

Description

 Action

1

Set Dimensions

• Set Preserve Aspect Ratio to keep the original format.
• e.g. setting the target to 50% reduces in this example the file size from 130 MB to 32 MB
• Set e.g. Percentage

2

Save the image 

file name like *_i_c_DBE_ABE_BN_RS.xisf

3

Keep the preview window

it will be reused in the next step.