Download and install the latest version of Filestar.
Right click on one or more J2c file(s) on your desktop and select Convert with Filestar.
Type convert to g4 in the search box.
Press Convert.
Or let an AI agent do it: filestarcli -i photo.j2c -c "convert to g4" (how).
Documents - File Explorer─☐✕
This PC › Documents
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.j2cContract.j2c
.xlsxBudget.xlsx
.pdfReport.pdf
.pngLogo.png
Filestar*Help✕
Drop files here to get started
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Let your AI agent convert J2C to G4
Claude Code, Codex, Cursor and other agents can do this on your computer with Filestar. Your files stay on your machine.
Install Filestar and add it to your agents:
npm install -g filestar
filestarcli agent install
Then ask your agent:
“Convert the J2C files in my Downloads folder to G4”
Or run it yourself:
filestarcli -i photo.j2c -c "convert to g4"
Runs on your computer, so your files stay on it. Works on Windows, macOS and Linux. 50 free conversions with the npm install, no account needed.
Can my AI agent convert J2C to G4?
Yes. Install the Filestar CLI with npm install -g filestar and your agent can run filestarcli -i photo.j2c -c "convert to g4" on your computer, so your files stay on it.
The JPEG 2000 Code Stream (j2c) file format is a type of image file format that is part of the JPEG 2000 family of image standards. This format is specifically designed for encoding images in a highly efficient manner, allowing for both lossless (exact reproduction) and lossy (approximate) compression. The j2c format focuses on the core coding stream of JPEG 2000 images, representing the encoded image data without additional metadata or structure.
Group 4 (G4) used for black and white lossless compression to maintain high-quality images, commonly used in TIFF format compression by fax machines. A picture is seen as black dots and lines on a blank page; the fewer the dots and lines are, the lesser the file size.
