Comments on: I’m looking for a replacement for “truecolor”

By: Nash

Nash — Thu, 12 Nov 2009 19:58:39 +0000

For the sake of discussion:

At least, thought of it in terms of if the image has a numerical Z-axis , or if the Z-axis is categorical.

An RGB Image is a multi-channel intensity image.
A grayscale image is a single channel intensity image.

An indexed image is a single channel(usually) color image – the effectively categorical Z values. Of course, there could be intensity information mapped by matching categories to intensity bins, but that is additional information not necessarily contained in the image.

In any case, this is a semantic issue – I just tend to define an image based on what it is made up of, rather than whether it is a ‘color image’ in the colloquial sense.

By: Steve

Steve — Thu, 12 Nov 2009 14:27:25 +0000

Nash—I don’t agree. Or perhaps I just don’t understand your point. A color image represented in multichannel form is not indexed.

By: Nash

Nash — Thu, 12 Nov 2009 14:25:11 +0000

A color image is Indexed, it is an image made up of colors.

By: Steve

Steve — Thu, 12 Nov 2009 13:13:31 +0000

Nash, Oliver, Yipeng—Thanks very much.

I’m intrigued by the idea of just using “color image.” When a distinction needs to be made between the common representations, we could say that a color image is either multi-channel or indexed.

By: Yipeng

Yipeng — Thu, 12 Nov 2009 11:59:24 +0000

I like “multi-channel image” or, simply, “colour image”.

By: Oliver Woodford

Oliver Woodford — Thu, 12 Nov 2009 10:47:51 +0000

Or “discrete-vector color” for integer type images.

By: Oliver Woodford

Oliver Woodford — Thu, 12 Nov 2009 10:46:49 +0000

real-vector color

By: Nash

Nash — Thu, 12 Nov 2009 07:58:06 +0000

I’d say “Spectral unit”,”Spectral pixel” or to make it snazzier “Lambda pixel” makes sense to me, since in an RGB image, each pixel contains a tiny representation of the light spectrum it is supposed to simulate. This is also general enough to take into account non-RGB images such as those Gene Dial mentioned.

On a similar note, we often refer to Grayscale images as Intensity images.Thus you can decompose a ‘spectral image’ into many intensity images, each representing a certain band of wavelengths.

By: Steve

Steve — Wed, 11 Nov 2009 23:58:49 +0000

Gene—Thanks very much, that’s useful info. I had forgotten about that use of the term “true color.”

By: Gene Dial

Gene Dial — Wed, 11 Nov 2009 23:00:45 +0000

GeoEye multi-spectral satellite imagery is available in Blue, Green, Red, and Near-Infrared bands. Image products can be produced in RGB, NRG, and BGRN band combinations. (NRG products have satellite NIR in the red TIFF position, satellite red in the green TIFF position, and satellite green in the blue position of the TIFF files.) We use “true color” for RGB products, “false color” or “color infra-red (CIR)” for NRG products , and “4-band” to describe BGRN products (delivered as 4-band TIFF files). A “color” product can be RGB, NRG, or BGRN. Use of this taxonomy has simplified our ordering, production and delivery processes and so may be useful in other contexts.
–Gene Dial, Director of Product Engineering, GeoEye Inc.