Auto Opacity Slider for Aseprite

Auto Opacity Slider for Aseprite

Auto Opacity Slider is a simple yet powerful Lua script designed to automate opacity animations. Instead of manually changing the opacity for every single frame, this script allows you to create smooth transitions (fades) between two values across a selection of frames in seconds.

Features

• Dual Sliders: Set a starting opacity and an ending opacity (0-255).
• Selection-Based: Works only on the frames you have selected in your timeline.
• Linear Interpolation: Calculates a perfectly smooth transition between your two chosen values.
• Safety Checks: Includes error messages if no sprite is open or if you try to apply it to a background layer.
• Undo Support: The entire process is wrapped in a single transaction (one Ctrl+Z undoes everything).

How to Use

1. Select your frames: In your timeline, highlight the range of frames you want to animate (they must be blue).
2. Select your layer: Make sure you are on the layer you want to modify.
3. Run the script: Go to File > Scripts > Auto Opacity Slider.
4. Adjust & Apply: Move the sliders to your desired min/max opacity and click Apply.

Installation

1. In Aseprite, go to File > Scripts > Open Scripts Folder.
2. Copy the AutoOpacity.lua file into that folder.
3. Go to File > Scripts > Rescan Scripts Folder (or restart Aseprite).
4. The script will now appear in your Scripts menu!

Important Notes

• This script modifies Cel Opacity, not the Alpha channel of individual pixels. This is non-destructive and preserves your original color data.
• The script requires at least 2 frames to be selected.
• Does not work on "Background" layers (right-click your layer and select Layer from Background to unlock opacity).