Colors Colors can be made of mixtures of

Colors • Colors can be made of mixtures of 3 primary colors. • If the medium is illumination (like on the face of a CRT) the colors are often called Red, Green and Blue. • If the medium is absorption (like paint or ink) the colors are often called Magenta, Yellow and Cyan (what some of us call red, yellow and blue). • In the Analog world, the saturation range can be very smooth. Computer Screen Colors 1

Digital Colors • In digital systems (for example in computer screens) there is a stepwise range of saturation for each of the 3 colors. • Many modern systems allow for 256 levels of saturation ranging from 0 (black) to 255 (brightest) for each of the three colors. • This can not be demonstrated in black and white print but running the program “colors. exe” in the class directory allows you to examine it. Computer Screen Colors 2

Digital Colors • This illustrates the appearance of an orange colored plate with a blue saturation of 0, a green saturation of 152/256 and a red saturation of 250/256 • With 256 shades of each of 2 colors, a total of 16, 777, 216 different colors are available. This color #39162. Computer Screen Colors 3

Digital Colors • A better understanding can be achieved if we look at the color numbers as binary values. • The binary system is the basis of the numbers and symbols used in a computer. • Binary numbers have just two values (0, 1) and computer switches and logic gates also have two values (on, off) Computer Screen Colors 4

Binary & Hexadecimal Numbers Dec. • • 8 4 2 1 Hex. 0 1 2 3 4 5 6 7 0 0 0 1 1 0 0 1 1 0 1 0 1 0 1 2 3 4 5 6 7 Dec. • • Computer Screen Colors 8 9 10 11 12 13 14 15 8 4 2 1 Hex. 1 1 1 1 0 0 1 1 0 1 0 1 8 9 A B C D E F 5

Decimal and Hexadecimal • The color to the right, Dark. Cyan, is made up of 139 parts of blue and 126 parts of green. • In Hex those numbers are 8 B and 7 E. • In binary they are 10001011 and 01111110. • This is color number 9, 141, 760 decimal or 8 B 7 E 00 hexadecimal. Computer Screen Colors 6

A Binary Exercise • • The binary number 10001011 base 2 is identical to 139 base 10. In the decimal world, the number 139 can be written as: • In the binary world the same procedure yields: 1 X 100 = 100 3 X 10 = 30 9 X 1 = + 9 Total 139 Computer Screen Colors 1 x 128 0 x 64 0 x 32 0 x 16 1 x 8 0 x 4 1 x 2 1 x 1 Total = 128 = 0 = 0 = 8 = 0 = 2 = + 1 = 139 7

A Hexadecimal Exercise • In the binary world the number 139 works out: 1 x 128 0 x 64 0 x 32 0 x 16 1 x 8 0 x 4 1 x 2 1 x 1 Total = 128 = 0 = 0 = 8 = 0 = 2 = + 1 = 139 • In the hexadecimal world, the number 8 B yields: 8 x 16 = 128 B or 11 x 1 = +11 Total = 139 Computer Screen Colors 8

The Number of a Color • Thus the color whose decimal number is 9, 141, 760 has a hexadecimal number of 8 B 7 E 00. • It is nearly impossible to determine the color from the decimal number but easy from the hexadecimal number. Computer Screen Colors 9

Coding Color into Visual Basic • In the hexadecimal world the decimal equivalent to 8 B 7 E 00 is: 8 8 x 1048576 B 11 x 65536 7 7 x 4096 E 14 x 256 0 0 x 1 Total = = = = 8388608 720896 28672 3584 0 + 0 9141760 Computer Screen Colors 10

Coding Color into Visual Basic You can use these numbers in your programs. A line of code in Visual Basic like: Label 1. Back. Color = 9141760 or: Label 1. Back. Color = &H 8 B 7 E 00 will make the background of Label 1 Dark. Cyan. Computer Screen Colors 11

The Internet and Color • The Internet uses a different format for colors. • Rather than the Blue-Green-Red that Visual Basic uses, the Internet uses Red-Green-Blue. • So color 8 B 7 E 00 hex or 9, 141, 760 dec in Visual Basic becomes color 007 E 8 B hex or 32, 395 dec on the Internet. • The problem is handled internally, you will see no problem. Computer Screen Colors 12