How to Import and Apply HaldCLUT in GIMP

HaldCLUT (High-dimensional Color Look-Up Table) images provide an efficient way to transfer complex color grades and film simulations between different applications. This guide explains how to import, grade, and map a HaldCLUT identity PNG image onto your photographs in GIMP using the G'MIC plugin. By following these steps, you will learn how to generate an identity file, apply adjustments to it, and map the resulting lookup table to achieve consistent, non-destructive color styling across your images.

Prerequisites

GIMP does not natively map HaldCLUT PNG files by default. You must install the free G'MIC-Qt plugin (GREYC's Machine for Image Computing) to access HaldCLUT creation and mapping filters. Once installed, it appears under the Filters menu in GIMP.

Step 1: Obtain an Identity HaldCLUT PNG

An identity HaldCLUT is a neutral grid representing the unaltered RGB color space.

  1. Open GIMP and navigate to Filters > G'MIC-Qt.
  2. Type Hald CLUT into the search bar.
  3. Select Colors > Generate Hald CLUT.
  4. Choose your preferred bit-depth and level (Level 8 generates a 512x512 PNG, which provides high fidelity).
  5. Click Apply to generate the identity pattern on your canvas.
  6. Go to File > Export As... and save the file as an uncompressed PNG (e.g., identity.png).

Step 2: Create Your Color Grade

To define the color transformation, you apply adjustments directly to the identity HaldCLUT:

  1. Open your identity.png file in GIMP.
  2. Use GIMP's color adjustment tools (Colors > Curves, Levels, Color Balance, or Hue-Chroma) to modify the image.
  3. Do not use spatial filters (such as blurs, sharpening, or grain), as HaldCLUTs only map pixel-to-pixel color data.
  4. Once satisfied with the color shifts, go to File > Export As... and export the modified file as a new PNG (e.g., grade_style.png).

Step 3: Map the HaldCLUT to Your Target Photo

To apply the saved color grade to your final photograph:

  1. Open the photo you wish to color grade in GIMP.
  2. Open Filters > G'MIC-Qt.
  3. In the search box, type Apply Hald CLUT and select Colors > Apply Hald CLUT.
  4. In the settings panel on the right, click the file browser icon next to the Hald CLUT Image field.
  5. Select your graded PNG file (grade_style.png).
  6. Adjust the Interpolation (choose Trilinear for smoother transitions) and set the Strength slider according to your preference.
  7. Click Apply or OK to execute the color mapping onto your photograph.