Curve

Diffusion output tends to run hot - oversaturated, high-contrast, a little too punchy compared to an actual photograph. The standard fix in photo editing has always been a tone curve: remap shadows, midtones, and highlights independently instead of just dragging a single contrast or saturation slider. Curve brings that exact tool into your graph, four channels (overall + R/G/B) at once, so you can flatten contrast a touch or push a color cast without leaving ComfyUI.

How it works

Each channel - all (affects everything), plus r, g, and b separately - gets three control points, each defined by an x (input tone, 0–255) and y (output tone, 0–255). The node maps input pixel values through this curve: a point sitting on the diagonal (input equals output) does nothing; move a point's y value above or below its x value and you're brightening or darkening that part of the tonal range. It's the same three-point curve tool from any photo editor, just exposed as numbers instead of a draggable graph.

The inputs and outputs that matter

Twelve numeric fields, one image input, one image output. All twelve follow the same pattern per point: an _x_point_N and _y_point_N pair, for N in 1–3, across four channel prefixes:

• all_* - global tone curve, affects every channel together. Point 1 sits around the shadows (default 63/63), point 2 around midtones (127/127), point 3 around highlights (191/191).
• r_*, g_*, b_* - the same three-point structure, but applied to a single color channel. This is where color grading actually happens: push a channel's midtone y-value up and that color gets stronger in the midtones; pull it down and the opposite color dominates.

The defaults for every point sit exactly on the diagonal (x equals y at all three points), which means out of the box this node does nothing - you have to move a y-value away from its x-value to see any change. Think of it as "point 1 = shadows, point 2 = midtones, point 3 = highlights," and nudge one at a time rather than all twelve at once.

How to install it

Search ComfyUI-HakuImg in ComfyUI Manager, or:

cd ComfyUI/custom_nodes
git clone --recurse-submodules https://github.com/licyk/ComfyUI-HakuImg

Restart ComfyUI, then look under Image → HakuImg. Pure pixel math, no models, no GPU dependency.

Common issues & troubleshooting

Changed the numbers, nothing happened. Double-check you moved a y_point value, not the x_point. Moving x alone just shifts where on the input range the curve bends, without changing whether it bends up or down - it's the y value that actually alters brightness/color.

Trying to flatten oversaturated diffusion output. Pull all_y_point_2 (the midtone point) down slightly from its default of 127 to reduce overall contrast, and consider a very slight push on r/b in opposite directions for a subtle warm or cool cast - that combination is the standard "make it look less like a raw render" move.

There's no visual curve widget. Unlike Photoshop, you're setting numbers, not dragging a line on a graph. If you're used to eyeballing a curve visually, it helps to sketch the shape you want on paper first (or just move one point, generate, look, repeat) rather than trying to set all three points blind.