18 April 2021

The sRGB book of color

2021-04-19T15:53:22-04:0018 April 2021|Categories: Image processing|

This page is inspired by the Munsell book of color. It aims at showing the sRGB gamut volume (all the visible colors that can be encoded as sRGB triplets), projected into a perceptually uniform lightness/chroma space (using JzAzBz color space[^1]), and sliced across hue planes. The sRGB space is the lowest common denominator of all [...]

21 March 2021

Rotation-invariant Laplacian for 2D grids

2021-05-23T09:47:52-04:0021 March 2021|Categories: Calculation|

NOTE : this article is a work in progress and not finished yet. ## Introduction The Laplacian operator $\Delta u$ is the divergence of the second-order partial derivative $\nabla^2 u$ of a multivariate function, which represents the local curvature of this function. This operator is widely used for edge-detection[^1], as well as in [...]

26 February 2021

9 April 2020

16 March 2020

Bilinear interpolation on images stored as Python Numpy ndarray

2020-04-01T11:10:54-04:0016 March 2020|Categories: Image processing|Tags: , |

If you are working in image processing and using Python as a prototyping script language to test algorithms, you might have noticed that all the libs providing fast image interpolation methods (to either sub-sample or over-sample) work in 8 bits unsigned integers (uint8). This is quite annoying if you are working with floating point images. [...]

17 January 2019

Derivating HDR-IPT direct and inverse transformations

2021-03-06T14:45:06-05:0017 January 2019|Categories: Image processing|

Following my work on the filmic tonemapping, several users have reported issues with very saturated blue areas (stage spotlights, bright skies) and red areas. The grail of image processing is being able to affect colors and brightness independantly. The big conundrum of tonemapping is raising luminance without affecting perceptual colors, and, by color, [...]

30 November 2018

28 September 2018

5 May 2018

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