Repository navigation
rgb(r,g,b) color strings silently paint white instead of the requested color #50
Description
Summary
fill_rectangle(color="rgb(40,180,90)") returns {"status": "success"} and paints white instead of the requested green. Nothing errors, so a caller cannot detect the failure except by inspecting pixels.
rgb() is documented as supported. From the fill_rectangle docstring:
color: Fill color (CSS name, hex, or rgb() string)
and new_canvas:
fill: ... Any CSS color name or hex string: "white" (default), "black", "transparent", "#FF5733", "rgb(100,200,50)", etc.
Reproduce
new_canvas(800, 400, name="t", fill="white")
# black frame first, so that a white fill is actually visible
fill_rectangle(x=540, y=80, width=200, height=160, color="#000000", layer_name="t")
fill_rectangle(x=580, y=110, width=120, height=100, color="rgb(40,180,90)", layer_name="t")
Both return {"status": "success"}. The second paints a white rectangle inside the black one.
get_pixel_color(640, 160, layer_name="t") then returns #ffffff.
The white-on-white case is nastier: on a default white canvas the same call looks like a complete no-op, so the failure is entirely invisible.
Root cause
Colour strings are passed straight to Gegl.Color.new() at roughly twenty call sites in gimp-mcp-plugin.py (1469, 2309, 2377, 2513, 2712, 2766, 2792, 2826, 2864, 2901, 2929, 2961-2962, 2971-2972, 3057, 3106, 3184, ...). Gegl.Color.new() does not accept rgb(r,g,b) syntax and, on a parse failure, returns a default colour instead of raising — so the error is swallowed.
Hex (#RRGGBB) works correctly.
This is the same underlying cause as #44 (CSS colour names resolving to cyan); only the fallback colour differs by input format.
Suggested fix
One _parse_color(s) -> str helper, used everywhere, that:
- normalises
rgb(r,g,b)and CSS colour names to#RRGGBBbefore handing off toGegl.Color.new(), and - raises on anything it cannot parse, so the tool returns
{"status": "error"}rather than painting the wrong colour.
The silent-wrong-colour behaviour is the dangerous part: a batch job reports success across hundreds of images while producing wrong output.
Environment
- GIMP 3.2.4, Windows 10, per-user install
- plugin:
gimp-mcp-plugin.py@ 09bfb2d - server: mcp 1.10.1 / fastmcp 2.10.1 on Python 3.13
Activity