Hi Pierpaolo,

I imagine Matlab would use intensity, but I never used it to build gabors.

You can find functions to create gabor patches using Psychtoolbox for Matlab: http://psychtoolbox.org/

If you want to use them for illustrative purposes, you can use the related functions (you can use GarboriumDemo to investigate them) and you will get a sensible result. If you are using them for research purposes, you will need to include calibration information (see PsychCal functions from the toolbox).

Good luck,

Leticia

Hi Leticia, I would like to understand which color space is used for reference and how color axes are modulated. I didn't find any reference for that. I hope your suggestions may be helpful for my purpose

Gabor patches are computer-generated visual objects that are used in experiments concerning human vision. They seek to model the cause and effect relationship between a wide range of visual stimuli and the cognitive summation in the brain by which we classify analyse and interpret our environment. They might be used for example to isolate investigate and model the visual perception of vertical, horizontal or tilted line orientation in an observed scene. The clear intent is to relate any given perception closely to a specific pattern of neuron activity in the brain. The ultimate objective is to use such components to build intelligent machines with human-like analytical and interpretive capabilities. Thus in imaging and image analysis, Matlab coding is widely used to model capabilities such as object and motion detection and to enable robot navigation. In order to ‘navigate’ in three-dimensional colour space it is first necessary to specify its basic perceptual dimensions. The intuitive option is to specify colour in terms of its perceived Hue Chroma (or purity or intensity) and Lightness. In the relevant Matlab model these parameters may in turn be further quantified by means of proprietary models such as Adobe Photoshop, or at a greater depth and numeric precision by using CIE Standard Observer Colorimetry (there are readily available introductions to both models on the internet).

Hi Pierpaolo,

in general, when it comes to colour spaces your choice depends on what you want to test. Gabor patches are often used to control cone-opponent low-level mechanisms (second-stage mechanisms). For this reason, colour is typically modulated along the axis of cone-opponent spaces, such as DKL and, less common for this purpose, MacLeod-Boynton. However, you can also use Gabor patches to investigate paradigms that require the control of colour appearance (i.e. how colours appear to the observer), such as the use of Gabor patches and the control of salience in attention research. In this case, you would rather use colour appearance models, such as CIELUV, CIELAB, CIECAM02. I add a little overview on colour contrast, where Gabors are modulated along the cone-opponent axes.

I hope this is of any help. All the best,

Christoph

Hi Pierpaolo (and others interested),

You can properly do it with the toolboxes COLORLAB and VISTALAB (see links below).

COLORLAB allows you to select meaningful color directions in properly formulated tristimulus or color appearance spaces and apply the proper calibration for accurate display.

VISTALAB allows you to control spatio-temporal sampling and define controlled Gabors.

COLORLAB: http://isp.uv.es/code/visioncolor/colorlab.html

VISTALAB: http://isp.uv.es/code/visioncolor/vistalab.html