ComfyUI Channel Ops (live-preview)

Comfyui custom nodes that modifies image channels with various per-channel operations across RGB, HSV, and Oklab color-space, aswell separate image blending node with live-previews

Note: Destination parameter has no effect on any operations other than Overwrites

Channel Ops

| Operation | Amount | Notes | |-----------|--------|-------| | Invert | – | Flip selected channel(s); Hue wraps. | | Overwrite | – | Copy Source into Destination (cross-space allowed). | | Overwrite from Image | – | Same as Overwrite but Source comes from 2nd image if connected. | | Set | x/255 | Set Source to Amount. | | Add | x/255 | Add Amount to Source. | | Subtract | x/255 | Subtract Amount from Source. | | Multiply | raw | Multiply Source by Amount (2 → 2×; 255 → 255×). | | Divide | raw | Divide Source by Amount (2 → ÷2). | | Clamp Min | x/255 | Clamp Source ≥ Amount. | | Clamp Max | x/255 | Clamp Source ≤ Amount. | | Truncate | 1−x/255 | Snap to step size. | | Contrast | 1−x/255 | Piecewise contrast around 0.5 (Oklab a/b normalized). |

| Source | Type | Notes | |--------|------|-------| | RGB | group | Applies to R,G,B together. | | R / G / B | single | One RGB component. | | HSV | group | Operates in HSV; Hue wraps on arithmetic. | | H / S / V | single | One HSV component. | | Oklab | group | L,a,b in perceptual space; a/b normalized to ±0.4 for some ops. |

| Destination | Type | Behavior | |-------------|------|----------| | R / G / B / H / S / V | single | Write scalar Source value into that component. | | RGB / HSV / Oklab | group | If Source group matches, copy full vector; else map scalar (HSV: h wraps; Oklab: L=scalar, a/b from normalized scalar). |

Notes

• “Overwrite from Image” uses the second image when connected; size and batch auto-align.

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Layer Blending

Modes (sRGB per-channel)

| Mode | Behavior | |------|----------| | Normal | B | | Multiply | A·B | | Screen | 1 − (1−A)(1−B) | | Overlay | A≤0.5: 2AB; else: 1−2(1−A)(1−B) | | Soft Light | (1−2B)A² + 2BA | | Hard Light | Overlay with B driving | | Darken / Lighten | min(A,B) / max(A,B) | | Color Dodge / Burn | A/(1−B) · clamp; 1−(1−A)/B | | Linear Dodge (Add) / Linear Burn | A+B; A+B−1 | | Vivid Light | B<0.5: Color Burn(A,2B); else: Color Dodge(A,2B−1) | | Linear Light | A + 2B − 1 | | Pin Light | B<0.5: min(A,2B); else: max(A,2B−1) | | Difference / Exclusion | |A−B|; A+B−2AB | | Add / Subtract / Divide | A+B; A−B; A/B | | Hard Mix | threshold(A+B) | | Darker Color / Lighter Color | Choose pixel by total brightness (sum RGB) |

Compositing & alignment

| Aspect | Rule | |--------|------| | Opacity | Out = A·(1−α) + Blend(A,B)·α | | Resize | Foreground bilinearly resized to background H×W | | Batch | Align to min(B) | | Clamp | Final result clamped to [0,1] |

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License

MIT