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File formats of Vector Images

aullah — Wed, 01 Feb 2012 13:47:11 +0000

In the previous article we learn about some advantages and a few drawbacks of vector image format. Vector graphics is the creation of digital images through a sequence of commands or mathematical statements that place lines and shapes in a given two-dimensional or three-dimensional space. In terms of physics, a vector is a representation of both a quantity and a direction at the same time. Today we will learn about the file formats that come under the name of vector graphics. But before that we will see what are the applications that can handle the making of vector images.

Applications that can handle the vector images

There are hundreds of applications on the market that can be used to create or modify vector data. In prepress, Adobe Illustrator and Corel Draw are the most popular programs.

File formats included in vector graphics

In the following you will see a list of image formats that are considered as vector images:

WMF (Windows Metafile)
CDR (CorelDraw)
DXF (AutoCAD)
SVG (Scalable Vector Graphics)
PLT (Hewlett Packard Graphics Language Plot File)
EPS (Encapsulated PostScript)
PDF (Portable Document Format)
PSD(Photoshop document)
AI(Adobe Illustrator)
DXF(Drawing eXchange Format)

In the next article we will learn about each of these file formats in a little detail.
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Advantages and Disadvantages of Vector Images

aullah — Wed, 01 Feb 2012 13:31:06 +0000

In the previous article we learn about the file size of vector images. We also discussed where these particular types of images are more suitably used. Today we will learn some advantages and disadvantages of these images.

Advantages of Vector images:

Vector images have a number of advantages over bitmap images, including:

The most important and obvious plus point of vector images is their power of scalability. If you try to enlarge a bitmap image, your computer can only enlarge the size of the squares making up the image area. That is why bitmap images get jagged as you enlarge them. However on the other hand the vector images remain smooth because your computer merely re-computes the coordinates of the points and adjusts the vector equation constants.
Each set of lines in a vector image represent separate and distinct objects. therefore every object can be re-edited at any time. For example, let’s say you created a vector art file with a circle in the background. You could open the drawing file at any time – even days later – and change the circle to a square.
Another very important reason of using vector images instead of bitmaps is their size. Vector images are much smaller in size than the bitmap image format. If you had a very large picture – such as a poster on your wall – the vector file might only take up a few kilobytes of space on your computer, while the same image in a medium resolution bitmap format might not fit on a CD-ROM!

Some disadvantages

However there are some disadvantages of these images as well. A few are as follow:

Drawings containing trapping information can only be scaled up to 20 percent larger or smaller.
Thin lines may disappear if a vector drawing is reduced too much.
Small errors in a drawing may become visible as soon as it is enlarged too much.
Another important disadvantage of vector is the time and talent needed to create it. You cannot take a photograph in vector. Vector images are drawn on the computer by a graphic artist using vector editing software such as Adobe Illustrator.
Because of the above mentioned reason the vector graphics are not as cost effective as bitmap images.

In the next article we will learn about the file formats that are supported by the vector image format.
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File Size of Vector Images

aullah — Wed, 01 Feb 2012 13:26:03 +0000

In the previous article we learn some facts about the vector images. We now know that unlike the pixelated bitmap images the vector graphics are made up by the mathematical calculations. Today we will lean how this particular feature of vector images affect the file size of these file formats.

File size of vector images:

Vector drawings are usually pretty small files because they only contain data about the Bézier curves that form the drawing. The EPS file format that is often used to store vector drawings includes a bitmap preview image along the Bézier data. The file size of this preview image is usually larger than the actual Bézier data themselves.

As we discussed earlier the vector images make it possible to define an image with very little information. This feature of vector graphics makes the file weight quite small. Moreover unlike the bitmap images the quality of vector graphics is not dependent on the screen resolution of the monitor screen of the viewer. They look alike on all screen resolutions.

How scaling is done in vector images:

When an illustration (drawing) program sizes a vector image up or down, it simply multiplies the mathematical description of the object by a scaling factor. For example a 1″ square object would need to be multiplied by a factor of 2 in order to double in size. The math is simply recalculated to produce an object twice the size of the original.

Where vector images can be used

As we have discussed earlier the vector images are highly salable, therefore they are often used to create logos. A vector logo can be easily scaled down to fit on a business card, or scaled up to fit on a tradeshow display, the side of a van or bus, or larger without losing quality.
Vector images can also have transparent backgrounds, making them easy to place or layer on top of other graphics.

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Vector Images

aullah — Mon, 30 Jan 2012 12:42:01 +0000

In the previous articles we learn about the bitmap images. Although they take the entire major file formats under their name, but there is still another major category of image format that is also used in web designing graphics. Today we will learn about the vector image formats.

Vector images:

Vector images are quite different from the bitmaps. As told earlier the bitmap images are made up of pixels but the vector graphics are not made of pixels, instead mathematical formulas called “lines and curves” form shapes that in turn make up a vector image. In this case the computer therefore does not read a list of coloured dots but it look up at the mathematical formula that creates these shapes.

Vector images are the graphical representation of geometrical entities such as circles, rectangles or segments. You can enlarge the vector images as much as you want, you will never see a single pixel.

Vector images are represented by mathematical formulae. A few examples are as follows:

A rectangle is represented by two dots.
A circle by a centre and a radius
A curve by several points and an equation

The computer processor will translate these mathematical calculations into such an information that a can be interpreted by the graphics card.

Vector images are created through the process of drawing with vector illustration programs such as CorelDRAW or Adobe Illustrator. The word “vector” is a synonym for line. Vector images can also be created through the process of conversion from a raster image by using a raster to vector conversion program such as CorelTRACE or EuroVECTOR. The most common vector image you come in contact with every day, is type. The type you are reading on the screen right now is vector based.

However you’ll need to have a fundamental understanding of raster images versus vector images to work successfully in any graphics package.

In the next article we will learn about some of the types of vector images that are commonly used these days.

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Advantages and Disadvantages of Bitmap Images

aullah — Mon, 30 Jan 2012 12:27:27 +0000

In the previous articles we learn about the file formats that come under the name of Bitmap images. Today we will learn the advantages and some disadvantages of these type of file format.

Bitmap Advantages

Following are some of the benefits of using the bitmap images:

Bitmaps are very easy to create. Take a picture with a digital camera, or scan something in, and you’ve got one.
Bitmaps are fairly simple to output, as long as your RIP or printer has sufficient memory.
They are easy to come by.
They are very cost effective. You can take a picture or scan in a drawing, and easily show it on the Internet or send in an email.
A bitmap image uses solid color pixels, which can be identified and recolored easily.
The geographic location of each cell is implied by its position in the cell matrix. Accordingly, other than an origin point, e.g. bottom left corner, no geographic coordinates are stored.

Bitmap Disadvantages

However bitmap images have some drawbacks too. A few common disadvantages of these format are as follows:

The most common and obvious disadvantage of these image format is that they are not upward scalable. You can make a bitmap smaller without to much loss, but you cannot make it larger without loosing quality. If you ever see a bitmap image blown up, you’ll notice it has little individual squares or dots that make up the image. When you see it at its optimal size you don’t notice the individual dots, but if you try to make it bigger, the image become fuzzy, jaggy or pixelated.
Another disadvantage of bitmap images is that they require higher resolutions and anti-aliasing for a smooth appearance.
The bmp file has been created by microsoft and ibm and is therefor very strictly bound to the architecture of the main hardware platform that both companies support.

That is all about the Bitmaps. The next few article will be dedicated to the second category of images: i-e the vector images.

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File formats of Bitmap Images(Cont. )

aullah — Mon, 30 Jan 2012 12:14:59 +0000

In the previous article we learn a few file formats that are supported by the Bitmap images, but they were not all. In the following you can see some more types of images that come under the name of Bitmap.

PDF:

PDF stands for Portable Document Format, PDF is a versatile file format that can contain just about any type of data including complete pages, it is not yet widely used to exchange just images. PDF is a file format developed by Adobe Systems. PDF captures formatting information from a variety of desktop publishing applications making it possible to send formatted documents and have them appear on the recipient’s monitor or printer as they were intended. To view a file in PDF format, you need Adobe Reader, a free application distributed by Adobe Systems.

PICT

PICT is an image file format that can contain both bitmap and vector data but that is mainly used on Macintosh computers and is not very suitable for prepress. PICT image format was developed by Apple Computer in 1984. PICT files are encoded in QuickDraw commands and can hold both object-oriented images and bit-mapped images. It is supported by all major graphic programs that run on Macintosh computers. The original PICT format supported 8 colors. However modern PICT including the new PICT2 format support 32 but color which results in more than 16 million colors.

PSD:

PSD files are the native file format of Adobe Photoshop (which can also contain vector data such as clipping paths).

TIFF:

TIFF images are a popular and versatile bitmap file format. TIFF stands for tagged image file format, one of the most widely supported file formats for storing bit-mapped images on personal computers. TIFF graphics can be of any resolutions and they can be black and white, gray scaled, or color. Files in TIFF format often end with a .tif extension.

In the next article we will learn about some advantages and disadvantages of Bitmap images. Later we will move on to the vector images.

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File formats of Bitmap Images

aullah — Mon, 30 Jan 2012 12:08:49 +0000

In previous articles we learn the various types of bitmap images. We understand the differences between each bitmap image category with the help of examples. Today we will learn all the file formats that come under the name of Bitmap image formats.

File formats that are used for bitmap data

Bitmap data can be saved in a wide variety of file formats. Following are the file formats that come under the name of Bitmap image formats:

BMP:

BMP is the standard bit-mapped graphics format used in the windows environment. By convention graphic files in the BMP format end with a .bmp extension. BMP images are an outdated and limited file format that is not suitable for use in prepress.

EPS:

EPS stands for Encapsulated PostScript. Pronounced as separate letters, EPS is the graphics file format that is used by the post script languages. EPS files can be either binary or ASCII. The term EPS usually implies that the file contains a bit-mapped representation of the graphics for the display purposes. In contrast, PostScript files include only the PostScript commands for printing the graphic. EPS is a flexible file format that can contain both bitmap and vector data. However it is gradually being replaced by PDF.

GIF

GIF stands for graphics interchange format a bit-mapped file format used by the World Wide Web CompuServe and many BBSs. GIF supports 256 color and various resolutions. It also includes data compression, but because it is limited to 256 colors, it is more effective for scanned images such as illustrations rather than color photos. Generally they are pronounced as giff or jiff. GIF images are mainly used for internet graphics etc.

JPEG:

JPEG images are mainly used for internet graphics. JPEG stands for Joint Photographic Experts Group, and pronounced jay-peg. JPEG is a lossy compression technique for color images. Although it can reduce files sizes to about 5% of their normal size, some quality and detail is lost in the compression.

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Types of Bitmap Images

aullah — Mon, 30 Jan 2012 12:01:54 +0000

In the previous article we learn about the factors that affects the weight of any bitmap image.

Types of bitmap images

Bitmap images can contain any number of colors but there are four main categories:

Line-art images:

The images that contain only two colors are called line-art images. Mostly the images made up of only white and black colors are called line-art images. Sometimes these images are referred to as bitmaps because a computer has to use only 1 bit (on=black, off=white) to define each pixel.

Grayscale images,

Gray scale images are those which contain many shades of gray. Pure Black and white colors are also included in these images. Typically 256 shades of gray (8-bit) are used even though the human visual system needs only 100 tints to perceive an image as life-like.

Multitones:

Multitone images are those picture that consist of two colors. But these colors can be of any shade. There is no restriction of gray, black or white color. such The most popular multitone images are duotones, which usually consist of black and a second spot color (often a Pantone color).

Full color images.

These images can contain all colors, and any possible combination of colors. The color information can be described using a number of color spaces: RGB, CMYK or Lab for instance.

Applications that can handle bitmap data

There are hundreds of applications on the market that can be used to create or modify bitmap data. In prepress, one application – Adobe Photoshop – completely dominates the market. This doesn’t mean that cheaper alternatives like Corel Photo-Paint, should be disregarded.

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File Size of a Bitmap Image

aullah — Mon, 30 Jan 2012 11:59:27 +0000

In the previous article we learn about the colors in bitmap images, and how the display of these images is affected by monitor screen resolution of the viewer. Today we will learn about the file size of this format of images.

File size of Bitmap images

In general Bitmap images are very large and heavy file formats. They can take up a lot of room. A normal Bitmap picture that is compressed for medium level quality takes up 40 MB. However the size of Bitmap images can be reduced by the process of compression but the quality will be compromised then.

Formula to calculate the size of Bitmap images

Following formula is used to calculate the exact file size of any bitmap image.

File size in kilobytes = Resolution2 x Width x Height x Bits per sample ÷ 8,192

From the above mentioned formula now we can understand all the factors that affects the weight of any image. The screen resolution, width and height of the image must be adjusted accurately in order to minimize the weight of the image.

Example:

For example, if you have a 4-by-5-inch, 1-bit image at 300 ppi, you know that the file size is 220 K (3002 x 4 x 5 x 1 ÷ 8192). A 24-bit image of the same size would be 5,273 K (just about 5 MB). In case you were wondering, this formula works because 8,192 is the number of bits in a kilobyte.

Designing tools# size calculator

However you do not need to calculate the weight of the image manually all the time. Almost all the image editing software have the size calculator within them. For example mostly the web designers use Adobe Photoshop for creating and editing the images. In Photoshop when you go to image and then the Image Size dialog box, they are handy calculator for determining the size and weight of any bitmap image.

For faster loading speed of your website you need to keep track of all these factors that counts for the weight of any image. Higher resolutions (dpi) and greater color depths, produce bigger file sizes. A typical 2″ by 3″ 150 dpi black and white raster image logo will be less than 70k (.07 megabytes) in file size. The same file saved as a 300 dpi 24-bit (millions of colors) raster image logo might be 100 times larger (over 7 megabytes).

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Colors of Bitmap Images

aullah — Fri, 27 Jan 2012 12:55:50 +0000

In the previous article we learn the structure of Bitmap images. Today we will learn two more characteristics of Bitmap images.

Colors of Bitmap images:

As discussed before there is a color palette in bitmap images. A BMP color palette is an array of structures that specify the red, green, and blue intensity values of each color in a display device’s color palette. Bitmap images support a pixel color depth running from 1-bit through 24-bit. A 1-bit color depth refers to a monochrome (black and white) pixel. A 1-bit BMP image is made up of pixels that can contain a value of either 0 (representing black) or 1 (representing white). The resulting image will therefore be black-and-white.

Each pixel in the bitmap data stores a single value used as an index into the color palette. The color information stored in the element at that index specifies the color of that pixel. A 24 bit BMP image is made up of pixels that are comprised of 256 possible states (or color gradients) each. The image is made up of a 256 x 256 pixel grid resulting in a total of 16,777,216 colors.

Interpolation

It is difficult to increase or decrease their size without sacrificing a degree of image quality. When you reduce the size of a bitmap image through your software’s resample or resize command, you must throw away pixels. When you increase the size of a bitmap image through your software’s resample or resize command, the software has to create new pixels. When creating pixels, the software must estimate the color values of the new pixels based on the surrounding pixels. This process is called interpolation.

Resolution dependency:

Bitmap images are resolution dependent. Resolution refers to the number of pixels in an image and is usually stated as dpi (dots per inch) or ppi(pixels per inch). Bitmap images are displayed on your computer screen at screen resolution: approximately 100 ppi.

A printer or scanner’s resolution is also measured in dots per inch. Typical desktop laser printers print at 300 – 600 dpi. Image setters are capable of printing over 2,500 dpi. Printers with higher dpi ratings are capable of producing smoother and cleaner output. The output quality of a printing device is dependent upon the resolution (dpi) of a bitmap or scan. A 300 dpi raster image will output at the same quality on a 300 dpi laser printer as on a 2,500 dpi image setter.

In the next article we will learn the file formats that are supported by the Bitmap images and the file size that is usually occupied by these type of images.

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