additive colors

Red, green, and blue colors (collectively called RGB) that televisions and computer monitors mix in various intensities to create all other colors. These are the actual (and not reflected) colors seen by the eye. Also called additive primary colors. See also CMYK color model and subtractive colors.

subtractive colors

   In four-color printing process, the CMYK colors (Cyan, Magenta, Yellow, and blacK) which are overlapped in various combinations and proportions to produce all other colors. The visible color is the reflected (and not the retained) color, and is called ‘subtractive’ because its wavelength is less than sum of the wavelengths of its constituting colors. See also additive colors.

Hue

Attribute of visual perception which is given names such as blue, green, purple, red, yellow, etc., according to the different wavelengths of light reaching the eye. A hue comprises of the appearance, brightness, and saturation of the perceived color.

Saturation

The amount of colour

To add more colour so its highly saturated   

take colour away to make it less saturated

Lightness

The act to making something lighter by adding more light to colour

gray scale

 Image whose each pixel can be black, white, or a shade of gray, because it is controlled by more than one bit of computer memory. As more bits are employed, the number of possible combinations grows exponentially. For example, if four bits control a pixel, the number of possible shades of gray is 16, with eight bits it becomes 256 shades.

Hexadecimal Colors

Red, Green and Blue

Hexadecimal numbers are used on web pages to specify colors.

The color is defined by its mix of Red, Green and Blue, each of which can be in the range:

0 to 255 (in decimal) , or
00 to FF (in hexadecimal)

 

  It is based on the idea that any color can be made by mixing Red, Green and Blue, and so it is called the “RGB Color System”.

It is also called an “Additive” color system, because it starts at black, and then color is added.

 

Hexadecimals

Hexadecimal numbers are “natural” to computers, because computers store and handle binary digits, and four binary digits make one hexadecimal digit (see Binary Digits):

Decimal: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Binary: 0 1 10 11 100 101 110 111 1000 1001 1010 1011 1100 1101 1110 1111
Hexadecimal: 0 1 2 3 4 5 6 7 8 9 A B C D E F

Two Hexadecimal digits together (called a “byte” in computer terminology) can represent 16×16=256 different levels of color.

pixel

 Picture element.’ Smallest square element of an image (mistakenly called ‘dot‘) that can be turned on (illuminated) or off (darkened) on a computer monitor. Detail (resolution) of an image depends on the number of pixels a monitor can show: VGA monitors display 640 x 840 (307,400) pixels per inch (PPI), SVGA monitors display 1,073 x 768 (786,432) PPI, and newer monitors can display 1,000 x 1,000 (one million) or more PPI. The number of colors that a monitor can display, however, depends on how much memory is assigned to each pixel. Two-bit memory pixels can show eight colors whereas eight-bit pixels can show 256.

alpha channel

In graphics, a portion of each pixel’s data that is reserved for transparency information. 32-bit graphics systems contain four channels — three 8-bit channels for red, green, and blue (RGB) and one 8-bit alpha channel. The alpha channel is really a mask — it specifies how the pixel’s colors should be merged with another pixel when the two are overlaid, one on top of the other.

Typically, you wouldn’t define the alpha channel on a pixel-by-pixel basis, but rather per object. Different parts of the object would have different levels of transparency depending on how much you wanted the background to show through. This allows you to create rectangular objects that appear as if they are irregular in shape — you define the rectangular edges as transparent so that the background shows through. This is especially important for animation, where the background changes from one frame to the next.

Rendering overlapping objects that include an alpha value is called alpha blending.

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