# Computer Graphics

The art is the rhythm of life. If there is no art, life becomes insipid. The graphics is a highly creative works in which imagination of artists bloom with different types of colors.

Generally, graphics is the combination of colors and imagination of uncanny caliber of artist on canvas. It is a medium of powerful expression. It is poetry of color and curves for illiterates or literates, and all.

### Image

Any picture including traditional scanned photographs can be called an image. Image make web page more alive but increases download time hence its use must be kept economical both in time and designing aspect.

#### Image Manipulation

Image manipulation is the actual process of altering image from original form. The image manipulation and processing both are different phenomena.

Presentation Software:

• Quick Show
• Museum
• Zed Card
• Gold Disk Astound
• Microsoft PowerPoint
• Kodak’s Arrange it

### Graphics

Pictorial representation of data is called Graphics. The term is broadly used in the world of digital arts, image processing, illustration, designing, animation and so on.

Graphics

There are two types of graphics:

(i) Bitmap: The graphics which is made up of fixed pixels is known as Bitmap graphics. It is a resolution-dependent graphics which cannot be scaled. It occupies more memory space and refresh rate of a screen containing bitmapped image is a faster than screen containing vector images.

Example:

Photographs, digital printings

(ii) Vector Graphics: The graphics created by lines and other geometrical shapes is termed as vector graphics. It is a resolution-independent graphics in which graphics are scaled easily without deformation. It occupies less memory space and refresh rate it more because at the time of refreshing computer recalculates vectors again. Cartesian coordinate system is applied to determine positions of pixels.

Example:

Line(x1, y1, x2, y2);

The first two arguments to the function specify the X and Y co-ordinates of the line’s starting points and the last two arguments specify the end points.

Example:

rectangle (int left, int top, int right, int bottom);

rectangle (50,10, 300, 200);

Example:

circle (int x, int y, int radius);

circle(250, 150, 100);

The center of circle is positioned at x-coordinate 250 and y-coordinate 150, and radius is made from series of 100 pixels.

Vector Graphics

### Image Processing

Image processing is a technique of creation, modification, storage and distribution of image as source of information. An image may be defined as a two-dimensional function, f(x, y); where x and y are spatial (plane) co-ordinates, and the amplitude f at any pair of co-ordinates(x, y) is called the intensity or gray level of the image at that point.

A digital image is a two-dimensional (2D) discrete signal. Mathematically, such signals can be represented as functions of two independent variables x and y. A monochrome digital image f(x, y) is a 2D array of luminance values,

Image Processing

with 0 <f(x, y) <L , and typically L =255. Each element of the array is called a pel (picture element), or more commonly a pixel. Typical image dimensions are M x N = 256 x 256 and 512 X 512.

• Steps evolved in image processing: Low level computer vision techniques overlap almost completely with digital image processing, which has been practiced for decades. The following sequence of processing steps is commonly recognized:

1. Image Acquisition: An image is captured by a sensor (such as a TV camera) and digitized, is called image acquisition.

2. Image Enhancement: To highlight certain features of interest in an image. A familiar example of enhancement is when we increase the contrast of an image because”it looks better”.

3. Preprocessing: computer suppresses noise (image pre-processing) and maybe enhances some object features which are relevant to understanding the image. Edge extraction is an example of processing carried out at this stage.

4. Compression: It is a technique for reducing the storage required to save an image or the bandwidth required to transmit it.

5. Image segmentation: computer tries to separate objects from the image background.

6. Object description and classification in a totally segmented image is also understood as part of low level image processing.

• Components of an Image Processing System: The image is a form of information.

1. Image Processing Software: There are many image processing software is available in market.

2. Mass Storage: An image of size 1024×1024 pixels, in which the intensity of each pixel is an 8 bit quality, requires one megabyte of storage space if the image is not compressed.

3. Image Display Unit: SVGA monitor

4. Hardcopy: Laser printers, film cameras, heat sensitive devices, inkjet units, optical and CD-ROM

5. Networks: The distribution of image through networks

### Graphics Tools

The Microsoft Paint is a beginners drawing canvas with many drawing tools, and colors. Most of us have learnt first lesson of drawing in Paint.

There are many graphic packages available in market in which Adobe Photoshop, CorelDraw, Macromedia Freehand etc are most popular for drawing and image editing purpose. All the packages have same foundation of graphics designing, painting and editing.

Graphic tool

The tools of graphics packages are similar in application and functions. Generally, all the packages contain five types of tools:

(a) Painting tools: Pencil, Airbrush, Paintbrush, Line, Bucket, Gradient, Rubber Stamp etc are painting tools used to paint drawings.

• Pencil tool: It is a free hand drawing tool with different tool with different types of strokes.
• Airbrush tool: It is used to spray droplets of colors of different diameters.
• Rubber Stamp tool: The rubber stamp tool samples, or pick up, an area of the image and then clones that area as you drag the pointer through the work area.
• Paint Bucket tool: It is used to fill color in the selected area. The area is selected using selection tools.

(b) Draw tools: Line, Rectangle, Ellipse, Rounded Rectangle, Polygon, Freeform etc are used to draw graphics on canvas of graphics packages.

• Line tool: It draws line.
• Rectangle tool: It is used to draw rectangle.
• Rounded Rectangle: For round corner rectangle.
• Ellipse: Used to draw circle or ellipse.
• Polygon tool: It is used to draw polygonal shapes.
• Custom Shape tool: It contains readymade shapes which are used for image effect.

Adobe Photoshop is a soul of artists, imagination of artists, thinking and philosophy of artists. The image processing software was developed by two brothers, john Knoll and Thomas in hobby and its early name was Display.

Draw Tool

Display become Photoshop 1.0 in 1990, which was released on a single floppy while it was a big hit from the beginning, it was not until version 4.0 that Photoshop achieved its cult status as ultimate in image editing, and stayed there ever since.

(c) Editing tools: Eraser, cropping, Marquee, Magic Wand, Lasso, Eyedropper, Smudge, Blur, Dodge, Focus, Toning etc are editing tools used to edit graphics.

• Eraser tool: it is used to erase extra pixels of images. The Background Eraser tool is used to remove background of image. The Magic Eraser tool is used to remove similar color in single click.
• Eyedropper tool: It is used to pick color from current images present on canvas or layer.
• Crop tool: It is used to select desired portion of images and discard rest part of images.
• Slice tool: It is used to make slice.
• Marquee tool: This tool enables you to select rectangular or elliptical areas by dragging a selection marquee in the image. There are Single row and Single column Marquee tools are also available for selection purpose.
• Lasso tool: It is used to draw freehand outline around an area to select image or objects. The Magnetic lasso and Polygonal lasso are available in Photoshop.
• Magic Wand tool: When positioned over a pixel, this tool selects adjacent pixels based on their color similarities.
• Blur tool: It causes image to appear softer and out of focus.
• Sharpen tool: This tool is just opposite to blur tool. It is used to increase pressure on pixels.
• Smudge tool: Smudge tool is used to soften the edges of images for a drop shadows effect by blending the edge colors.
• Dodge tool: Dodge tool is applied to block light from photographic print so that the white paper is protected from exposure, allowing the area to remain lighter. It has three options: Shadows, Midtones, and Highlights. The default type of dodge tool is Midtones.
• Burn tool: It is used to increase darkness.
• Sponge tool: It is used to increase or decrease color saturation. If image is drawn in grayscale color mode, sponge tool is used to change contrast value.

(d) Type tool: It is used to type text horizontally, vertically and in desired fashion. It has not capability of edit text like as word processing packages.

(e) Selection tools: Magic Wand, Lasso, Move, Rectangular and Elliptical Marquees etc are used to select whole graphics or targeted part of graphics for editing purposes. The selection tools are used to select specific area within graphics to add special effects, fill colors, remove colors, and remove selected portions and many other editing activities.

• Zoom tool: It is used to view selected portion or area of image zoom in or zoom out
• Move tool: It is used to move or rotate images on the canvas. It is also important to position layers at appropriate positions in the composite and complex types of images.
• Hand tool: used to drag sections of the image into view.

### Some Special tools

There are many software package dedicated for art works. The Macromedia Freehand, CorelDraw, and many other has following tools to provide special effects for graphics and texts.

• Emboss Tool: It is used to create a three- dimensioning effect in which the edges of images are raised or lowered so that the image appears to be embossed into the background.
• Envelope Tools: It is used to distort images and text block.
• Blend tool: It creates a series of intermediate objects between the two objects.
• Shadow Tool: A drop shadow is a copy of an object placed behind the original to give the illusion of light source.

### Canvas

The drawing area is termed as Canvas where color castes their effects to design graphics. It has minimize, maximize, and close button. Its size and background is determined when File > New command is activated. Its size can be increased while working with image also. This facility is provided in Image menu. The tool box and some essential palettes are also opened to help designer at the time of designing.

### Layers

The concept of layer is like as onion scales in which one scale is covered by next scales. The layer is used to design and edit complex graphics for the purpose of presentations and animation. The positioning, size control, rotation, and all type of editing works are done on the level of layer.

Some options for working with layers are given as:

(a) New Layer: It is used to create new layers.

(b) Duplicate Layer: If you have make duplicate of any layer with objects which, it is used.

(c) Delete Layer: Undesired layer is deleted using it.

(e) Merge Layers: If you have to merse layers, use it.

### Palettes

Palettes are essential components of tool sets. These palettes are used to define and customize the tools. These are some palettes of Photoshop:

• Info Palette
• Layer Palette
• Brushes Palette
• Command Palette
• Color Palette

All Palettes contain:

• A little bar with close and collapse buttons
• A set of tabs
• A list of options for each tab

### Designing Principle

Every professional art works are based on certain principles. These principles determine guide lines and prevent artists from extra aggregation.

Some important principles are following:

(a) Coherence:      (b) Balance:

(c) Proportion:       (d) Rhythm:

(e) Repetation:      (f) Variety:

(g) Emphysis:        (h) Economy:

### Filters

Filter is the special effect used in graphics to modify appearance. It adds spice to Photoshop. It can fulfill the need of beginner as well as professionals. The first time user of Photoshop can just open an image and apply filters with single click.

Professional will be more serious and can create wonders out of it. Let us see the art, science and philosophy behind the filters. Before we proceed further it is necessary to mention that we are going to observe the features of the filters provided by Photoshop only. Third party filters is another vast subject need separate attention. Only registered third party filters should be used, otherwise system may be crashed.

#### So, what is filter?

Filters are the ready-made effects grouped under filter menu of Photoshop can be applied with single clicked either on the entire image or a selection. Photoshop 6.0 or more come up with rich variety of filters starting from artistic to digimarc. In general, filters are used to add special effects to image. It can be used for photo retouching. It is used to create realistic textures, stunning text effects. It can entirely change the environment of an image. Generally filters come up with the dialog box, which consist of small preview window and preview check box. Preview window will show the immediate effect of the filter on the image without actually applying on it. With the help of preview check box it can be seen applied on the original image also. Preview window provides another good facility. It pans an image so that you can see any part of the image and judge the effect of the filter on that particular part. The filter is applied on only selected or current layers. If you have to add effect to certain area, at first area should be selected using the Magic wand, the Lasso tool or the marquee tools.

Procedures:

• Select desired area using selection tools
• Choose desired settings if dialog box is displayed.
• Observe effects in Preview box and click OK

(a) Artistic: As a name suggest this filter is used to achieve artistic effects. You can get traditional fine arts effects with this filter. Effects resembles with natural and traditional artistic creations created with different types of brushes, strokes, colored papers, different styles of painting, posterized effects etc. It contains Colored Pencil, Cutout, Dry Brush, Film Grain, Fresco, Paint-Daubs, Palette Knife, Plastic Wrap, Poster Edges and many other effects to offer artistic touch to graphics.

Filters > Artistic > Cut Out

No. of Levels : 8

Edge Simplicity: 1

Edge Fidelity: 2

(b)Blur:  It is an important filter used for photo retouching work. Most of the time it is applied on scanned image. It is used to soften entire or the part of an image. In the technical word it can be explained like, it smoothens the transition between hard edge of an image. It has Gaussian Blur, Motion Blur, Radial Blur, Smart Blur effect to accomplish bluring of graphics.

Filters > Blur > radial blur

Blur Method: Spin

Quality: Good

(c) Brush Strokes: it is similar to artistic filters but more using brush strokes and ink effects generating traditional fine art type of output.

Filters > Brush Strokes > Angled Strokes

Direction Balance: 50

Stroke Length: 3

Sharpness: 3

(d) Distort: These filters takes times to apply hence require more memory for smooth working. It distorts images and creates reshaping effects.

Filters > Distort > Ripple

Amount: 100%

Size: Medium

(e) Noise: Noise is extra pixels which affect appearance of image. Images are often degraded by random noise. Noise can occur during image capture, transmission or processing, and may be dependent on or independent of image content. This is a very popular filter among Photoshop users. It is useful in creating textures. It adds grains to provide the base for textures. Other filters in this groups like median, dust & Scratches, despeckle are used extensively for photo retouching.

Filters > Noise > Add Noise

Amount: 18%

Distribution: Uniform

Monochromatic

(f) Pixelate: It creates small cells in an image based on similar color.

Filters > Pixelate > Facet

(g) Render: If you want to work with light reflections, cloud like patterns, this is the right choice. This is a powerful filter providing different option for lighting effects and clouds. It contains 3D Transform, Clouds, Difference Clouds, Lens Flare, and Lighting Effects.

Filters > Render > Lighting Effects

(h) Sharpen: It sharpens the soft edges by increasing the contrast of the pixels.

Filters > Sharpen > Sharpen

(i) Sketch: It is similar to artistic as it creates traditional fine art effects. It resembles much with hand drawn looks when it is applied on an image.

Filters > Sketch > Water Paper

Fiber Length: 3

Brightness: 50%

Contrast: 50%

(j) Stylize: It is used to create impressionistic effects.

Filters > Stylize > Diffuse

Mode: Normal

(k)Texture: It is used to create textures. It gives realistic look like sand, paper etc. to an image.

Filters > Texture > Texturizer

Texture: Sandstone

Scaling: 100%

Relief: 4

Light Direction: Top

(l) Video: It is used to smoothen the images captured on videos. It contains De-Interlace and NTSC Colors effects.

(m) Other: This is used to create your own filters. The Custom, high Pass, Maximum, Minimum, Offset etc are available effects.

(n) Digimarc: It is used to add digital watermark to an image which is essential for copyright information.

#### Some Technical Terms

Some important technical terms applied in Graphics packages are described here:

(a) Brightness/Contrast: The brightness and contrast is used to increase or decrease brightness. This facility is available in all the graphics software. In Photoshop, it is included in Image menu.

Image > Adjustments >Brightness/Contrasts. . .

(b) Opacity: The opacity is related with intensity of images drawn or placed on layer. When its value is decreased (1%), image or layer becomes transparent. When its value is 100%, image or layer becomes opaque.

(c) Mask: It is used to include some portion of image and cancels rest portion. It makes possible to apply effects to selected portion of layers. The mask covered and protected parts of an image.

(d) Channel: It is used to store color information about an image or to store selection. Photoshop creates color information channels automatically and all Photoshop images contain at least one channel.

(e) Feather: The feather is a process to reduce extra pixels from edges of selected area.

Procedure:

We open image file or select layer or part of image for feather effect.

• Select > Feather
• Enter the value for a feather Radius, and click OK.

(f) Slice: A slice is rectangular area of image that is used to create links, rollovers, and animation for web pages.

### Some other terms:

• Foreground color: Alt + Backspace
• Background color: Ctrl + Backspace
• Watermark: The image with low opacity is called watermark and it is suitable as background images.
• Anti-aliasing: It is a term used to remove rough pixels from the edge of images. These rough pixels are present like as saw-teeth (jagged) or ladder fashion at the edge portion of images.

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