`image_grayscale`

Convert a single image to grayscale.

Parameters

pathstringone of path or source_key: Source image path
source_keystringone of path or source_key: Context key containing a source path, artifact URI/descriptor, or explicit Base64 object
output_pathstringrequired: Destination image path
formatstringdefault inferred / png: png or jpeg/jpg
output_keystringdefault "grayscale_image": Prefix for output values

Artifact inputs are opened and SHA-256 verified inside the tracked blocking worker; decoding consumes that same rewound handle rather than a resolved store pathname.

Supported source formats are BMP, Farbfeld, GIF, HDR, ICO, JPEG, PNG, PNM, QOI, TGA, TIFF, and WebP. Output remains restricted to PNG or JPEG.

Context Output

<output_key> — output file path
<output_key>_width / <output_key>_height
<output_key>_format
<output_key>_success

Example

local flow = Flow.new("image_grayscale_demo")

flow:step("grayscale", nodes.image_grayscale({
    path = "examples/fixtures/ironflow-sample.png",
    output_path = "output/sample_front_gray.png",
    output_key = "gray"
}))

flow:step("log", nodes.log({
    message = "Grayscale image: ${ctx.gray_width}x${ctx.gray_height}"
})):depends_on("grayscale")

return flow

Resource contract

Image headers and decoded byte requirements are checked before allocation using IRONFLOW_MAX_IMAGE_ENCODED_BYTES (50 MiB), IRONFLOW_MAX_IMAGE_PIXELS (25 million), and IRONFLOW_MAX_IMAGE_DECODE_ALLOCATION_BYTES (128 MiB). The working estimate includes retained source plus grayscale output. Decode, grayscale conversion, and encode run on a tracked blocking worker with cancellation checkpoints between opaque operations.