Preprocess on Astro Live Stacker

Hot Pixel Removal

Sun, 31 May 2026 06:32:34 +0000

Overview

The HotPixelRemove process removes hot pixels from the image.

Its configuration is managed via ALS preferences.

Configuration

	Source	Data Type	Required	Default
ON/OFF	Preferences: Processing Tab	ON/OFF	∅	OFF

Control

This process is controlled by the Preprocess pipeline.

Input

Data	Type
image provided by the Preprocess pipeline	Image

Behavior

graph LR

START([START])

TEST_ENABLED{{Process enabled?}}
TEST_COLOR{{Color image?}}

COMPUTE[Compute average value of neighbors of each pixel]
REPLACE[Replace hot pixel value with the average of its neighbors]

RETURN[Return modified image]
UNCHANGED[Return unchanged image]

END([END])

START --> TEST_ENABLED
TEST_ENABLED -->|Yes| TEST_COLOR
TEST_COLOR ---->|Yes| UNCHANGED
TEST_ENABLED ---->|No| UNCHANGED
TEST_COLOR -->|No| COMPUTE
COMPUTE --> REPLACE
REPLACE --> RETURN
RETURN --> END
UNCHANGED --> END

classDef bounds fill: #333, stroke: #666, stroke-width: 2px, color: #BBB, font-family: 'Poppins', sans-serif
classDef step fill: #444, stroke: #622, stroke-width:2px, color: #c6c6c6, font-family: 'Poppins',sans-serif
classDef wait  fill: #444, stroke: #262,stroke-width: 2px, color: #c6c6c6, font-family:'Poppins', sans-serif
classDef test fill: #444, stroke: #226, stroke-width: 2 px, color: #c6c6c6, font-family: 'Poppins', sans-serif

class START bounds
class TEST_ENABLED test
class TEST_COLOR test
class COMPUTE step
class UNCHANGED step
class REPLACE step
class RETURN step
class END bounds

Each pixel in the image whose value deviates too much from its neighbors is considered a hot pixel.

Dark Subtraction

Sun, 31 May 2026 06:32:34 +0000

Overview

The DarkRemove process subtracts the thermal noise from the image using a user-provided master dark.

Its configuration is managed via ALS preferences page.

Configuration

	Source	Data type	Required	Default value
ON/OFF	Preferences: Processing Tab	ON/OFF	∅	OFF
Master dark path	Preferences: Processing Tab	File path	Yes	∅

Control

This process is triggered by the Preprocess pipeline.

Input

Data	Type
image received from the Preprocess pipeline	Image
master dark read from configured path	Image

Behavior

graph LR

START([START])

TEST_ENABLED{{Processing enabled?}}
TEST_SIZE{{Identical dimensions?}}
TEST_TYPE{{Identical data types?}}

CONVERT[Convert master dark]
SUBTRACT[Subtract master dark from image]

RETURN[Return modified image]
UNCHANGED[Return unchanged image]

END([END])

START --> TEST_ENABLED

TEST_ENABLED ----->|No| UNCHANGED
TEST_ENABLED -->|Yes| TEST_SIZE

TEST_SIZE ----->|No| UNCHANGED
TEST_SIZE -->|Yes| TEST_TYPE

TEST_TYPE -->|No| CONVERT
TEST_TYPE -->|Yes| SUBTRACT

CONVERT --> SUBTRACT
SUBTRACT --> RETURN

RETURN --> END
UNCHANGED --> END

classDef bounds fill: #333, stroke: #666, stroke-width: 2px, color: #BBB, font-family: 'Poppins', sans-serif
classDef step fill: #444, stroke: #622, stroke-width:2px, color: #c6c6c6, font-family: 'Poppins',sans-serif
classDef wait  fill: #444, stroke: #262,stroke-width: 2px, color: #c6c6c6, font-family:'Poppins', sans-serif
classDef test fill: #444, stroke: #226, stroke-width: 2px, color: #c6c6c6, font-family: 'Poppins', sans-serif

class TEST_ENABLED,TEST_SIZE,TEST_TYPE test
class START,END bounds
class RETURN,UNCHANGED,CONVERT,SUBTRACT step

The master dark is subtracted from the image.

Debayering

Sun, 31 May 2026 06:32:34 +0000

Overview

The Debayer process is used on color images in FITS or Raw format.

It generates a color image from the raw image and the description of the Bayer pattern installed on the sensor that generated the image.

Its configuration is managed via ALS preferences page.

Configuration

	Source	Data Type	Required	Default Value
Bayer pattern	Preferences: Processing Tab	choice: - AUTO - GRBG - RGGB - GBRG - BGGR	YES	AUTO

Control

This process is triggered by the Preprocess module.