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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.

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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.

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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 is color #39162.

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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)

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Binary & Hexadecimal Numbers

Dec. 8 4 2 1 Hex.

• 0 0 0 0 0 0• 1 0 0 0 1 1• 2 0 0 1 0 2• 3 0 0 1 1 3• 4 0 1 0 0 4• 5 0 1 0 1 5• 6 0 1 1 0 6• 7 0 1 1 1 7

Dec. 8 4 2 1 Hex. • 8 1 0 0 0 8• 9 1 0 0 1 9• 10 1 0 1 0 A• 11 1 0 1 1 B• 12 1 1 0 0 C• 13 1 1 0 1 D• 14 1 1 1 0 E• 15 1 1 1 1 F

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Decimal and Hexadecimal

• The color to the right, DarkCyan, is made up of 139 parts of blue and 126 parts of green.

• In Hex those numbers are 8B and 7E.

• In binary they are 10001011 and 01111110.

• This is color number 9,141,760 decimal or 8B7E00 hexadecimal.

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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:

1 X 100 = 100 3 X 10 = 30 9 X 1 = + 9 Total 139

• In the binary world the same procedure yields:

1 x 128 = 128 0 x 64 = 0 0 x 32 = 0 0 x 16 = 0 1 x 8 = 8 0 x 4 = 0 1 x 2 = 2 1 x 1 = + 1 Total = 139

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A Hexadecimal Exercise

• In the binary world the number 139 works out:

1 x 128 = 128 0 x 64 = 0 0 x 32 = 0 0 x 16 = 0 1 x 8 = 8 0 x 4 = 0 1 x 2 = 2 1 x 1 = + 1 Total = 139

• In the hexadecimal world, the number 8B yields:

8 x 16 = 128B or 11 x 1 = +11 Total = 139

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The Number of a Color

• Thus the color whose decimal number is 9,141,760 has a hexadecimal number of 8B7E00.

• It is nearly impossible to determine the color from the decimal number but easy from the hexadecimal number.

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Coding Color into Visual Basic

• In the hexadecimal world the decimal equivalent to 8B7E00 is:

8 8 x 1048576 = 8388608 B 11 x 65536 = 720896 7 7 x 4096 = 28672 E 14 x 256 = 3584 0 0 x 16 = 0 0 0 x 1 = + 0 Total = 9141760

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Coding Color into Visual Basic

You can use these numbers in your programs. A line of code in Visual Basic like:

Label1.BackColor = 9141760

or:

Label1.BackColor = &H8B7E00

will make the background of Label1 DarkCyan.

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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 8B7E00 hex or 9,141,760 dec in Visual Basic becomes color 007E8B hex or 32,395 dec on the Internet.

• The problem is handled internally, you will see no problem.