Vector Graphics

CS404

Not CS425 in 3 days! Software and Hardware technologies used in a computer system to create, modify, and display still images stored in digital form. Jaye's browser story. Future is hard to predict. New technologies (LCD, Plasma, Laser, ...) Realigy overlay Virtual reality Holographic

Vector Graphics

Tektronix Storage Screen Graphics

Vector Graphics

Image is stored as a mathematical description of a collection of individual lines, curves, and shapes making up the image. Computation takes place during display. Can internally store vector graphics and then convert to bitmapped graphics before display.

Bitmapped Graphics

Image is modeled by an array of pixel values. In memory? Logical Pixels On screen? Physical Pixels By far the most normal hardware display technology currently in use.

Examples

Vector Flower

Vector Poppy

Vector Image Transformations

Transformed Poppy

Outlined Poppy

Bitmapped Flowers

Bitmapped Image Processing

Enlarge vector image

Enlarge bitmapped image

Graphics File Formats

Many Many “Encyclopedia of Graphics File Formats” describes nearly 100. To compress or not to compress. If compress, lossy or lossless. And how about color? Indexed? Full 32 bit? If indexed, which color table to use? Web friendly: GIF, JPEG, PNG Others: TIFF, BMP, TGA

GIF Originally developed by CompuServe. Lossless compression technique LZW. LempelZivWelch assigns fixed length code words to variable length sequences of source symbols but requires no a priori knowledge of the probability of occurrence of the symbols to be encoded. Restricted to 256 colors. Major patent problems with regard to LZW. Replacement > PNG?

JPEG Joint Photographers Experts Group Lossy compression based on DCT (Discrete Cosine Transform). Transform image to frequency domain and sort components by most important, then throw away least important components. JFIF – JPEG File Interchange Format specifies the compression. SPIFF is that officially endorsed file format for JPEG. (see www . jpeg . org

PNG

Portable Network Graphics (pronounced “ping” ). See www . libpng . org /pub/png/pngintro.html Replacement for GIF. Removes the problem with the patent by using a different compression technique. Not restricted to 256 colors. Supported by most web browsers.

TIFF

Tagged Image File Format Elaborate EXTENSIBLE file format that can sore full color bitmaps using several different compression schemes (including jpeg). Has the concept of a “tag” specifying a set of data related to the image. This allows for extensions to be bypassed if the reader doesn't recognize a tag. Often used where scaling is important.

BMP

BitMaP format. Microsoft Windows Bitmap format. Platformdependent. Only supports a simple form of lossless compression. Often stores uncompressed, (read LARGE).

TGA

Truvision Targa & Vista hardware. One of the earliest to support greater than 256 colors. If you convert the pgm files to tga files Adobe Photoshop can read them.

Vector Graphics File Formats

PostScript SVG SWF

PostScript

A programming language with builtin graphics capabilities that allow it to specify the appearance of pages in the form of a program describing how to place graphics elements – paths, shapes, and fills – on a page. I wrote a PostScript program to do the Sierpinski triangle.

%!PSAdobe2.0 %%Creator: dvips(k) 5.86 Copyright 1999 Radical Eye Software %%Title: exam1.dvi %%Pages: 10 %%PageOrder: Ascend %%BoundingBox: 0 0 596 842 %%EndComments %DVIPSWebPage: (www.radicaleye.com) %DVIPSCommandLine: dvips o exam1.ps exam1.dvi %DVIPSParameters: dpi=600, compressed %DVIPSSource: TeX output 2003.10.08:1009 %%BeginProcSet: texc.pro

%%Page: 1 2 1 1 bop 147 631 a Fd(1.)49 b(\(4)37 b(p)s(oin)m(ts\))g(Using)g(the)h (follo)m(wing)c(co)s(de)k(to)f(de\014ne)i(a)e(3D)g(ob)5 b(ject,)39 b(sk)m(etc)m(h)h(the)e(ob)5 b(ject)38 b(on)f(the)272 751 y(axes)c(b)s(elo)m(w.)44 b(Lo)s(cate)32 b(and)h(lab)s(el)e(an)m(y)i (v)m(ertices)h(y)m(ou)f(use)g(on)g(the)g(diagram)d(y)m(ou)k(create.)272 1021 y Fc(GLfloat)53 b(vertices[])h(=)d({)h(0.0,)g(0.0,)h(1.0,)1451 1142 y(0.0,)f(1.0,)h(0.0,)1451 1262 y(1.0,)f(0.0,)h(0.0};)272 1503 y(GLubyte)g(objectIndices[])i(=)d({)f(0,)h(2,)g(1)f(};)426 1743 y(glEnableClientState\(GL_VER)q(TEX_)q(ARRA)q(Y\);)426 1864 y(glVertexPointer\(3,)56 b(GL_FLOAT,)d(0,)f(vertices\);)426 1984 y(/*)f(object)i(*/)426 2105 y(glColor3f\(0.0,0.0,0.0\);)426 2225 y(glDrawElements\(GL_LINE_LOO)q(P,)k(3,)52 b (GL_UNSIGNED_BYTE,)k

EPS

Encapsulated PostScript Applies certain conventions to the use of PostScript to ensure that the images in an EPS file are selfcontained so that they can be incorporated in other documents.

3 W C SVG

Scaleable Vector Graphics format Defined in XML. A derivative of PostScript that uses the same imaging model but a fixed repertoire of operations and is thus easier to implement, and more compact for transmission over networks.

SWF

(pronounced “swiff” ) Macromedia Flash. Ad hoc standard. Used for vector animations.

All these (PostScript, SVG, and SWF) can also support bitmapped graphics as selfcontained objects. And many more, see encyclopedia contents.