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Digital Image

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on 18 September 2014

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Transcript of Digital Image

Digital Image
What is an Image?
It is a visual representation of an object using different techniques of design, photography, painting and video.
Digital images are those obtained by devices such as video cameras, cameras, cell phones, scanners or directly generated by computers.
How are they obtained?
There are two main ways of representation of images, that make the whole "digital images". On one side are the raster or bitmap and in the other hand, we have graphics or vector images.

> Bitmap Images (or raster images)
A pixel is each of the small areas or squares that compose a digital image. It can have millions of colours.
1. File Format
2. Weight or Volume
3. Dimension
4. Resolution
5. Color Depth

> 1. File Format
These formats save higher image quality but its weight is considerably greater.
tiff - psd - eps - bmp
jpg y png (alta calidad)
These formats can include editable vector graphics and fonts.
jpg - gif - png
16 bits
8 bits

Expresses the amount of information destined to represent the color of each pixel.
The color depth of an image is the number of different colors that can contain each of the points or pixels that form it, and depends on the amount of information (number of bits) that can store a pixel.
The higher the bit depth of an image, the greater the number of tones (grayscale or color) that can be represented, there will be more available colors and more exctly will be the color representation in the digital image. Digital images can be produced in black and white, grayscale or color.

1 bit (2 tones black or white) for px.
8 bits (256 colors or grey) for px.
RGB (Red, Green, Blue):
24 bits (images in color 16,7 millon of colors) for px.
CMYK (Cian, Magenta, Yellow, Black):
32 bits (only for quality printing)
Format: .jpg
Mode: RGB - 8 bits Weight: 155 Kb.
Format: .jpg
Mode: Escala de Grises 8 bits Weight: 127 Kb.
Format: .gif
Mode: indexado – 8 bits (256 colores)
Weight: 111 Kb.
Format: .png
Mode: RGB - 24 bits Weight: 167 Kb.
> 4. Resolution
The pictures produced from digital cameras are bitmaps, so the images that capture a scanner are too; in these images the highest quality they have (nº of pixels per unit of measure is determined at the moment of creating them so we can not extend the resolution or number of pixels per unit in the future, ie we can not extend the resolution without compromising image generally deformed and losing sharpness, because the pixels that compose them are modified.
A high resolution image can be extended and remains clear and detailed. Although his weight is greater considrablemente. (Eg 300 DPI image.)
In the same image in low resolution, pixels are seen at first sight (Pixelated) and image enlargement makes it confusing. (Eg 72 DPI image)
The resolution is inversely proportional to the size of an image (bitmap) If we take a bitmap image and we reduce to half its size, the resolution will be double.
If we take bitmap image and we increase its size to the double the resolution will decrease by half.
Example of compressed image; the original weight 207kb, has been changed the compression up to 11.16kb, if you look you can further reduce the weight of the picture, however the quality gets really bad.
Constructed images using bitmaps
The image appears with its edges serrated, which is corrected by the software generating an anti-alias, which makes look the image smoother.

The monitor will show them similar but the weight will be significantly smaller while having less dpi.
Format: .jpg
Resolution: 300 dpi
WEight: 1167 Kb. ó 1.14 Mb
Format: .jpg
Resolution: 72 dpi
Weight: 168 Kb.
Image processing software most used:

Picmonkey.com (online editor)
Pixlr.com (online editor)
Splashup (online editor)
> Vector Images
Vector images are made from vectors. Vectors are objects which are mathematically formed . A vector is defined by a serie of points that have some controllers which can handle the shape of the line created to be joined together. The main elements of a vector are Beizer curves. Vector images can be enlarged without distortion.
Vector image. Beizer curve. The curve is defined by the nodes or control points and controllers or handles that define and shape its form. To change these you just have to move the arrows until you get the desired curve.
By using the vector formats with mathematics coordinates to form concrete images the resolution of these is infinite, ie, any vector image can be scaled by zooming, without being concerned the visibility of it , or screen or when printing.
The vector image allows us to create varied line contours and define the color of the shapes that they create. The shape can be controlled very precisely and each object can be managed independently from the rest, because it is built with a own mathematical form.
Vector Images Formats
1 megapixel is 1 million pixels. The megapixel is often used to count the number of pixels that contains a digital picture and also to measure the resolution of digital cameras.

For example, a 3.1 megapixel digital camera can take pictures with a maximum resolution of 2048 x 1536 (ie 3,145,728 pixels)
The Bit and the color
The Bit and the color
It is about of the composition of the color image
Infinite scale
Scale Vector Graphics
Extensions generated by the Flash software. Optimal for animations underweight.
EPS is one of the best formats to be imported from most design software. It is a very adaptable format because we can use it also for vector image as a bitmap.
Its characteristics in the way of constructing graphs are the same as the program Corel Draw.
It is the format of the program that generates it. The graphs we do with Corel Draw are vector and are composed of lines and planes that are located in specific coordinates of the page.

> 5. Color Depth
pdf y swf
Color Depth

The end.
1920 x 1080 px.
2.1 MP
Screen sizes in px.
Digital Image
It is a computer file formed by a series of numerical matrices of zeroes and ones that are stored in computer memory and which define its characteristics.
Digital Images Categories
Each shape is composed of a set of cells contained in an orthogonal grid where each element is called a pixel (picture element)

> Factors that Define The Digital Image
Es uno de los formatos más conocidos y utilizados por su calidad y bajo peso de los archivos.
No acepta transparencias.
>| Formatos de imagen de mapa de bits para diseño de pantalla.
Es un formato gráfico que comprime sin pérdida de datos y de uso libre. Almacena imágenes con una mayor profundidad de color (hasta 24 bits). Permite almacenar transparencias
Este tipo de archivo se creó con la finalidad de obtener archivos de tamaño muy pequeños. Es recomendado para guardar imágenes NO fotográficas tales como: Logotipos, imágenes de colores planos, dibujos simples, etc. (8 bits-256 colores). Alacena transparencias. Permite animaciones (gif animado).
There are two generic types of format:
> File Format Types
Created by the same extension of the application that has created it and it can not be opened by any other program than the one that created it.
Which is appropriate to insert or read in diferent applications that the one that has created it.
to Export
.ai .psd
.jpg .gif .png
> 2. Volume or Weight
> 3. Dimension
The measures in pixels have an equivalence in measurement units to be used in the real world, eg cm, mt, etc.
Inversely proportional to the size of an image (bitmap)
You must use the appropriate resolutions for different uses of the image.
> 3. Dimension



Digital documents

Desktop documents

72 dpi

100 dpi
150 dpi
300 dpi (mínimo)
1 bit: Black and white
8 bits: 256 colors
16 bits: Thousand of colors
24 bits: 16,8 Millon of colors
32 - 64 bits: Many more
What is a Digital Image?
Every digital file has a format which is expressed as an extension of the document name, separated by a dot.
> 1. File Format
It corresponds to the amount of information expressed in binary code contained in the file.
Digital Archives = formed by 0 and 1
The smallest unit is the bit composed of 8 bits = 1 byte
1.024 bytes = 1 Kilo byte
1.024 Kb = 1 Mega byte 1.024 Mb = 1 Giga byte
> 3. Dimension
Digital files are represented by pixels, and the pixels constitute a unit of subjective image representation.
> 4. Resolution
The resolution is the "quality" of the image, expressed in density or number of pixels that linearly, take up the space of an inch. The unit of measurement of the resolution: dpi (dot per inch) ppi (pixel per inch) or dpi (dots per inch)
Weight-Quality Relationship
Display resolution is similar but it varies when printing
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