Color Test Chart Image

Some nodes exist to make pretty images. This one exists to make repeatable ones. ColorChartImageLoader loads a color test chart straight from the comfyui-jbnodes images/ folder - the pack ships three (512, 768, and 1024 px) - so you can see exactly what a filter, a grayscale conversion, or a film stock does to known colors instead of eyeballing a random photo.

This is the debugging instrument of the whole film pipeline. Want to know what the No. 25 red Wratten filter actually does to blues? Run the chart through FilterLab and compare. Want to see how the "Wet Plate Collodion" grayscale curve crushes everything but blue? Feed it the chart. Known input, predictable output - that's how you learn the knobs without guessing.

How it works

It's a loader with a very specific menu. The required image input is an enum listing whatever color_chart*.png files exist in the pack's images folder: color_chart_512.png, color_chart_768.png, and color_chart_1024.png ship by default. The node reads that directory at graph-build time, so if you drop your own color_chart_whatever.png into the folder and refresh, it shows up in the dropdown. That's a genuinely nice touch for people who want their own reference chart.

Output is a single image of type IMAGE. One selection, one output, no other knobs. About as simple as a node gets.

When to reach for it

Use it whenever you're comparing. Some examples that actually come up:

• Wire the chart into GrayscaleLab and A/B the five luminance methods to see which curve flattens or shifts which colors.
• Feed it into FilterLab with different Wratten filters to internalize what each one does to reds, greens, and blues.
• Chain it through the full camera pipeline (CameraLab → DeveloperLab → PrintLab) as a calibration reference for a specific film stock.

The 1024 version is the sharpest test target; the 512 is there if you want fast iterations. For actual "does this portrait look like Tri-X" work, use a real photo - the chart is for understanding, not aesthetics.

Install

Part of the pack:

cd ComfyUI/custom_nodes
git clone https://github.com/AlbertJBurton/comfyui-jbnodes.git
cd comfyui-jbnodes
pip install -r requirements.txt

Restart ComfyUI, or use ComfyUI Manager and search "comfyui-jbnodes." Dependencies: numpy, torch, colour-science, scipy, Pillow (Pillow is what actually reads the PNGs here).

Gotchas

• The dropdown only lists files whose names start with color_chart and end in .png/.jpg/.jpeg/.webp. Drop a file named mychart.png and it won't appear - name it color_chart_mychart.png.
• If the images folder is missing, the node creates it and falls back to a "none" entry until a chart exists; after an update, re-check that the bundled charts are still there.
• It's a beta pack - loader behavior and folder layout can shift between versions, though this one is simple enough to survive most changes.