DIGITAL’IMAGE’ · DIGITAL’IMAGE’ The’ Pixel’ (a word’ invented’ from’ "picture’ element")’ is’ the’ basic’ unit of’ programmable’color’on’acomputer

DIGITAL IMAGE

DIGITAL IMAGE The Pixel (a word invented from "picture element") is the basic unit of

programmable color on a computer display or in a computer image.

2 Mr. DE MIGUEL -‐ DIGITAL IMAGE

DIGITAL IMAGE

Bitmap images (imágenes en mapa de bits) are stored as a series of Jny

dots called pixels. Each pixel is actually a very small square that is

assigned a color, and then arranged in a paMern to form the image.

When you zoom in on a bitmap image you can see the individual pixels

that make up that image. Bitmap graphics can be edited by erasing or

changing the color of individual pixels using a program such as Adobe

Photoshop.

Mr. DE MIGUEL -‐ DIGITAL IMAGE 3

DIGITAL IMAGE Vector images (imagen vectorial) are not based on pixel paMerns, but instead

use mathemaJcal formulas to draw lines and curves that can be combined to

create an image from geometric objects such as circles and polygons. Vector

images are edited by manipulaJng the lines and curves that make up the image

using a program such as Adobe Illustrator


DIGITAL IMAGE What is the difference between bitmap and vector images?

hMp://www.bbc.co.uk/schools/gcsebitesize/dida/graphics/bitmapvectorrev1.shtml

hMp://www.bbc.co.uk/schools/gcsebitesize/dida/graphics/bitmapvectorrev2.shtml


DIGITAL IMAGE What is the difference between bitmap and vector images?


DIGITAL IMAGE

Bitmap graphics so\ware •  MS Paint •  Adobe Photoshop •  GIMP (Free so\ware)

Vector graphics so\ware •  Adobe Illustrator •  Adobe FreeHand •  CorelDRAW •  Pro/DESKTOP •  INKSCAPE (Free so\ware)

What is the difference between bitmap and vector images?


BITMAP IMAGE Bit depth (profundidad de bit)

The number of binary bits that define the shade or color of each pixel in a

bitmap. For example, a pixel in a black-‐and-‐white image has a depth of 1

bit, because it can only be black or white. The number of color values that a

given bit depth can produce is equal to 2 to the power of the bit depth. For

example, a bit depth of 1 can produce two color values (2 1 =2), and a bit

depth of 2 can produce 4 color values (2 2 = 4).


Color depth (Profundidad de color)

The maximum number of colors an image can contain. Color depth is

determined by the Bit depth of an image and the displaying monitor. For

example, an 8-‐bit image can contain up to 256, while a 24-‐bit image can

contain roughly up to 16 million colors. A GIF image is an example of an

8-‐bit image; a JPEG image is an example of a 24-‐bit image.

BITMAP IMAGE

Bit depth ranges between 1 to 64 bits per pixel (bpp), and determines

the color depth of an image.


BITMAP IMAGE bit depth


BITMAP IMAGE Bit depth

and Color depth


BITMAP IMAGE Bit depth


BITMAP IMAGE PROPERTIES

ResoluJon (Resolución)

The resoluJon of an image is an important factor in determining the aMainable output

quality. The higher the resoluJon of an image, the less pixilated it will be and the curves of

the image will appear smoother.

PPI (Pixels Per Inch) (Pixeles por pulgada)

A expression of the resoluJon of a conJnuous tone image. Basically the same as DPI.

DPI (dots per inch) (Puntos por pulgada)

DPI is the number of dots (or pixels -‐ PPI) that fit horizontally and verJcally into a one-‐inch

measure. The more dots per inch, the more detail is captured and the sharper the image

will appear.


Exposure (Exposición)

A measure of the amount of light in which a photographic image is recorded.

Overexposed images are lighter than normal; underexposed images are darker than

normal.

Brightness (Brillo)

The relaJve lightness or darkness of an image, the intensity of a light source, or color

luminance.

Contrast (Contraste)

The difference between light and dark areas in an image. Also describes the dynamic

range of an image. The wider the tonal range is in an image, the lower the contrast will

be.



Hue (Tono)

Hue is the actual color of an object. Hue is measured as a pure color (on the color

wheel) in degrees, for example degrees and variaJons of blue which define a green-‐

blue or sea-‐blue up to a purple-‐blue.

SaturaJon (Saturación)

SaturaJon is the color intensity of an image. A color with high saturaJon will appear

brighter and more vibrant than the same color with low saturaJon.




Color model

A system used to describe and reproduce color.

RGB

A color mode in which the three colors of light (red, green, and blue) are combined in

varying intensiJes to produce all other colors. A value between 0 and 255 is assigned to

each channel of red, green and blue. Monitors, scanners, and the human eye use RGB to

produce or detect color.

CMYK

A color mode made up of cyan (C), magenta (M), yellow (Y), and black (K). CMYK prinJng

produces true blacks and a wide tonal range. In the CMYK color mode, color values are

expressed as percentages; therefore, a value of 100 for an ink means that the ink is

applied at full saturaJon.


BITMAP IMAGE Lossy vs. Lossless compression (Compresión con o sin pérdida)

FORMATS

TIFF

A lossless file format that can be compressed. This format is widely supported

across operaJng systems. TIFF is the best file format for archiving high quality

images.

JPG or JPEG

The JPG file format was specifically created for photographs, and can contain

millions of colors. JPGs are automaJcally compressed (you can choose the level

of compression to match your desired image quality), resulJng in a relaJvely

small file size while sJll retaining quality. For this reason, JPGs are ideal for email

and Web use. JPGs are lossy, discarding informaJon each Jme that they are

compressed.


BITMAP IMAGE Lossy vs. Lossless compression

FORMATS

GIF

The lossless and compressed file format that is preferred for graphics, because it keeps

edges and lines sharp. GIFs are limited to 256 or fewer colors, and are not

recommended for photographs, but rather for images with flat fields of color, such as

clip art. GIFs can be staJc or animated

PNG

Portable Network Graphics format, an open source subsJtute for GIFs. PNGs provide a

higher lossless compression rate than GIFs, and help to reduce cross-‐plaqorm

differences in image display quality, among other technical advantages. PNG provides a

useful format for the storage of images during intermediate stages of ediJng.


BITMAP IMAGE


BITMAP IMAGE



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DIGITAL’IMAGE’ · DIGITAL’IMAGE’ The’ Pixel’ (a word’ invented’ from’ "picture’ element")’ is’ the’ basic’ unit of’ programmable’color’on’acomputer