Working with Photoshop
Photoshop is hailed as one of the best image-editing application
for raster graphic images. A raster graphics image, digital
image, or bitmap, is a data file or structure representing
a generally rectangular grid of pixels, or points of colour,
on a computer monitor, paper, or other display device. Raster
graphics are different from vector graphics, which use geometrical
primitives, such as points, lines, curves, and polygons to
represent images in computer graphics. The conversion between
pixels and inches is roughly 1” = 72 pixels or 1cm =
28 pixels.
Photoshop works with a number of different colour spaces:
* sRGB colour space
(white point=D65) – It is known as ‘RGB’(Red
Green Blue) in Photoshop. sRGB defines the red, green, and
blue primaries as colours where one of the three channels
is at the maximum value and the other two are at 0.
* Lab colour space (white
point=D50) – It is known as ‘Lab’
in Photoshop. Lab colour space is considered the most complete
colour model and has been used traditionally to describe all
the colours visible to the human eye.
* CMYK colour model –
It is a subtractive colour model used in printing. This model
is based on mixing pigments of Cyan, Magenta, Yellow, and
Key or black, (CMYK) in order to make other colours. The CMYK
colour model works through light absorption.
* Grayscale – In computing,
a grayscale image is defined as an image in which the value
of each pixel is equivalent to a single sample. The images
are typically composed of shades of gray, varying from black
at the weakest intensity to white at the strongest.
* The white point
is a number of reference, used to define the colour ‘white’
in colourimetry. This number varies in different applications,
as different definitions of white are needed to give acceptable
results.
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