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https://github.com/afichet/camera-calibration

Applications for camera colorimetric calibration using a Macbeth colorchecker.
https://github.com/afichet/camera-calibration

calibration color colorimetric colorimetry image-processing photography

Last synced: 29 days ago
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Applications for camera colorimetric calibration using a Macbeth colorchecker.

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README 

        
Building the toolkit

====================



First, checkout the repository:



```bash

git clone https://github.com/afichet/camera-calibration.git

cd camera-calibration

git submodule init

git submodule update

```



## Dependencies



On all platforms, you need CMake, a C and a C++ compiler.



### Windows and macOS



We compile levmar without BLAS / LAPACK to have simple compilation

pipeline on those platforms. You can re-enable it in the

`external/levmar-2.6/CMakeLists.txt` for better performances.



### Linux



You need f2c (`libf2c2-dev` on Ubuntu 20.04LTS), BLAS / LAPACK. See

http://users.ics.forth.gr/~lourakis/levmar/



## Compilation



```bash

mkdir build

cd build

cmake ..

make

```



Images

======



We currently support TIFF and EXR images for reading and

writting. TIFF are supported only if `libtiff` is available on the

system.



Applications

============



## Colourotron



`Colourotron` is a GUI application to fit a correction matrix from a shot of a 

Macbeth colourchecker. The source code is in the `app/gui` folder.



## Extract patches



`extract-patches` is used for creating a CSV file from an image and a

CSV containing the areas to average. The CSV file contains the top

left pixel and bottom right pixel for the box to extract.



```csv

, , , 

...

```



You can control which area are averaged using the `overlay-areas`

utility.



## Overlay areas



`overlay-areas` is used to display an overlay of the area that are

going to be averaged by `extract-patches` utility.



## Generate reference colorchart



`gen-ref-colorchart` is used to create a CSV file containing the XYZ

values of each color patch from reference measured data (available

here: https://www.babelcolor.com/colorchecker-2.htm) given an

illuminant and color matching functions (CMFs).



## Generate colorchart image



`gen-colorchart-image` creates a PNG preview of a given CSV file

containing color values of each patch of a Macbeth colorchecker.



## Fitting



`extract-matrix` fits a transformation matrix from a measured set of

colors to a reference set of colors.



## Correct patches



`correct-patches` corrects color values of each patches contained in a

CSV file using the provided transformation matrix.



## Correct image



`correct-image` corrects color values of each pixel from a TIFF or EXR

file using the provided transformation matrix.



## Conversion to DNG



`raw-to-dng` handles the propriatery RAW format this application targets and

outputs a standard DNG file. It requires a calibration matrix that can be

extracted using `Colourotron` fitting feature.



Pipeline example

================



We provide a pipeline example in `run.sh` script.



## GUI



### Colour calibration



This is the recommended solution.



Open your image with `Colourotron`. 

1- Move the Macbeth outline to match the captured Macbeth.

2- Click on `Fit...`. 

3- Click on `Apply`.

4- Save the matrix with `File -> Save correction matrix...`



This matrix can then be used with the command line tools.



### Demosaicing



To perform colour correction, you either can convert the propriatery RAW to DNG

or first debayer the image and apply the correction matrix. To debayer the 

image, use `derawzinator`:



```bash

./build/bin/derawzinator \

    raw_image_INFO.txt \

    raw_image.exr

```



### Colour correction



We can correct any given RGB image using the matrix:



```bash

./build/bin/correct-image \

    data/measurements/Colors_0000000320_dem.tiff \

    output/matrix.csv \

    output/corrected_image.tiff

```



You can also convert the propriatery RAW format to DNG:



```bash

./build/bin/raw-to-dng \

    raw_image_INFO.txt \

    output/matrix.csv \

    output/output.dng

```



## Command line



First, you need to extract from a TIFF file the values of the Macbeth

color checker. You need as well a CSV file (comma separated)

describing each area to average.



```bash

mkdir output



./build/bin/extract-patches

    data/measurements/Colors_0000000320_dem.tiff \

    data/measurements/boxes.csv \

    output/patches.csv

```



Then, you need to generate a reference set of Macbeth patches given an

illuminant and color matching functions:



```bash

./build/bin/gen-ref-colorchart \

    data/D65.csv \

    data/XYZ.csv \

    output/reference.csv

```



Now, let's see how this reference colour chart looks like:



```bash

./build/bin/gen-colorchart-image \

    output/reference.csv \

    output/reference.exr

```



And how the averaged measured one looks like:



```bash

./build/bin/gen-colorchart-image \

    output/patches.csv \

    output/orig_measured.exr \

	true

```



Now, we want to find the matrix which transform the measured color to

the reference colors:



```bash

./build/bin/extract-matrix \

    output/reference.csv \

    output/patches.csv \

    output/matrix.csv

```



Finally, we correct the measured patches:



```bash

./build/bin/correct-patches \

    output/patches.csv \

    output/matrix.csv \

    output/corrected_patches.csv

```



And, create an image of the corrected patches:



```bash

./build/bin/gen-colorchart-image \

    output/corrected_patches.csv \

    output/corrected_measured.exr

```



We also can correct any given image using the matrix, here the input

image:



```bash

./build/bin/correct-image \

    data/measurements/Colors_0000000320_dem.tiff \

    output/matrix.csv \

    output/corrected_image.tiff

```



You can also convert the propriatery RAW format to DNG:



```bash

./build/bin/raw-to-dng \

    raw_image_INFO.txt \

    output/matrix.csv \

    output/output.dng

```