Graphics File Formats

Graphics File FormatsGraphics File Formats

Graphics File Formats 2

Graphics DataGraphics Data Vector dataVector data

– LinesLines– PolygonsPolygons– CurvesCurves

Bitmap dataBitmap data– Array of pixelsArray of pixels– Numerical values corresponding to Numerical values corresponding to

gray-level or color of set of pixelsgray-level or color of set of pixels


Types of FormatsTypes of Formats Bitmap Bitmap

– TIFF, GIF, JPEGTIFF, GIF, JPEG VectorVector

– AutoCAD DXFAutoCAD DXF MetafileMetafile

– Can contain both bitmap and vector Can contain both bitmap and vector data in the same filedata in the same file

– Macintosh PICTMacintosh PICT


Types of FormatsTypes of Formats AnimationAnimation

– TDDD, TTDDDTDDD, TTDDD MultimediaMultimedia

– Apple QuickTimeApple QuickTime– MPEGMPEG


Types of FormatsTypes of Formats 3D3D

– Descriptions of shape and color of 3D Descriptions of shape and color of 3D object models (scene elements)object models (scene elements)

– Models placed in scenes with lights Models placed in scenes with lights and camerasand cameras

– Autodesk’s DXFAutodesk’s DXF– Used by rendering programs like Used by rendering programs like

Autodesk’s 3D StudioAutodesk’s 3D Studio


Types of FormatsTypes of Formats VRMLVRML

– Hybrid of 3D graphics and HTMLHybrid of 3D graphics and HTML AudioAudio VideoVideo FontsFonts


Pixels and CoordinatesPixels and Coordinates


DisplayDisplay Fewer colors than device can displayFewer colors than device can display


DisplayDisplay More colors than device can More colors than device can

displaydisplay


DisplayDisplay Quantization artifactsQuantization artifacts

– BandingBanding– Moire patternsMoire patterns– New colors not present in imageNew colors not present in image


PalettesPalettes 1-dimensional array of color values1-dimensional array of color values

– Color mapColor map– Index mapIndex map– Color tableColor table– Look-up tableLook-up table

Bitmap data in a file stored as series Bitmap data in a file stored as series of index valuesof index values– Pseudo-color storagePseudo-color storage


PalettesPalettes Can easily change, say, all red Can easily change, say, all red

pixels to greenpixels to green


PalettesPalettes Palette elementPalette element

– 24 or 32 bits24 or 32 bits

(0,0,0)(0,0,0)(255,255,255)(255,255,255)(255,0,0)(255,0,0)(0,255,0)(0,255,0)(0,0,255)(0,0,255)(255,255,0)(255,255,0)(0,255,255)(0,255,255)(255,0,255)(255,0,255)

(128,0,0)(128,0,0)(0,128,0)(0,128,0)(0,0,128)(0,0,128)(128,128,0)(128,128,0)(0,128,128)(0,128,128)(128,0,128)(128,0,128)(128,128,128)(128,128,128)(255,128,128)(255,128,128)


PalettesPalettes 320 320 200 image with 3 bytes of 200 image with 3 bytes of

color information per pixel and up color information per pixel and up to 256 colorsto 256 colors– Image without palette would take Image without palette would take

320*200*3 bytes of storage, or 320*200*3 bytes of storage, or 192,000 bytes192,000 bytes


PalettesPalettes 320 320 200 image with 3 bytes of 200 image with 3 bytes of

color information per pixel and up to color information per pixel and up to 256 colors256 colors– Image with 1 byte palette would take Image with 1 byte palette would take

320*200*1 + 256*3 (length of palette) 320*200*1 + 256*3 (length of palette) bytes of storage, or 64,768 bytesbytes of storage, or 64,768 bytes

– For small amounts of data, palette For small amounts of data, palette length could outweigh savings in color length could outweigh savings in color encodingencoding


Color SpacesColor Spaces Composite colors are defined by Composite colors are defined by

specifying three values for specifying three values for amounts of amounts of fundamental colors, fundamental colors, or or color channelscolor channels

Color is a point in Color is a point in color spacecolor space


Color SpacesColor Spaces RGBRGB

– Red, green, and blueRed, green, and blue– (R,G,B)(R,G,B)

(0%, 0%, 0%) is black(0%, 0%, 0%) is black(100%, 100%, 100%) is white(100%, 100%, 100%) is white(50%, 50%, 50%) is light gray(50%, 50%, 50%) is light gray(100%, 0%, 0%) is red(100%, 0%, 0%) is red(0%, 100%, 0%) is green(0%, 100%, 0%) is green(0%, 0%, 100%) is blue(0%, 0%, 100%) is blue


Color SpacesColor Spaces RGBRGB

– 24 bit RGB24 bit RGB Range is 0-255Range is 0-255

(0, 0, 0) is black(0, 0, 0) is black(255, 255, 255) is white(255, 255, 255) is white(127, 127, 127) is light gray(127, 127, 127) is light gray(255, 0, 0) is red(255, 0, 0) is red(0, 255, 0) is green(0, 255, 0) is green(0, 0, 255) is blue(0, 0, 255) is blue


Color SpacesColor Spaces TruecolorTruecolor

– Human eye can distinguish 2Human eye can distinguish 224 24 colorscolors– Device equal to or exceeding this is Device equal to or exceeding this is

said to display said to display truecolortruecolor– No palette neededNo palette needed

First byte is R, second byte is G, third First byte is R, second byte is G, third byte is B byte is B


Color SystemsColor Systems Additive color systemsAdditive color systems

– Adding colors to black creates new colorsAdding colors to black creates new colors– The more colors that are added, the The more colors that are added, the

closer to white we getcloser to white we get– Presence of all colors creates white, Presence of all colors creates white,

while absence of all colors creates blackwhile absence of all colors creates black– Additive color environments are self-Additive color environments are self-

luminousluminous Color on monitorsColor on monitors


Color SystemsColor Systems Subtractive color systemsSubtractive color systems

– Primary colors subtracted (absorbed) from Primary colors subtracted (absorbed) from white to create new colors (reflected)white to create new colors (reflected)

– The more colors that are subtracted, the The more colors that are subtracted, the closer to black we getcloser to black we get

– Presence of all primary colors creates black, Presence of all primary colors creates black, while absence of all primary colors creates while absence of all primary colors creates whitewhite

– Subtractive color environments are reflectiveSubtractive color environments are reflective Color on paperColor on paper


Color SystemsColor Systems RGBRGB

– AdditiveAdditive– Most widely usedMost widely used– For graphics monitorsFor graphics monitors


Color SystemsColor Systems CMYCMY

– Cyan-Magenta-YellowCyan-Magenta-Yellow– SubtractiveSubtractive– Used by most laser and ink-jet printersUsed by most laser and ink-jet printers– CMYKCMYK

K stands for black, which is treated K stands for black, which is treated independentlyindependently

Glossy magazinesGlossy magazines– A dot of composite color is a grouping of four dots, A dot of composite color is a grouping of four dots,

each one a CMYK coloreach one a CMYK color


Color SystemsColor Systems HSVHSV

– Hue-Saturation-ValueHue-Saturation-Value– HueHue

Specifies colorSpecifies color– SaturationSaturation

Called Called chromachroma Refers to amount of white in a hueRefers to amount of white in a hue

– Fully saturated hue contains no white and is pureFully saturated hue contains no white and is pure– Red hue with 50% saturation is pinkRed hue with 50% saturation is pink



– ValueValue Called Called brightnessbrightness How much light color emitsHow much light color emits Hue with high value is very brightHue with high value is very bright Hue with low value is blackHue with low value is black

– Color system used by paintersColor system used by painters Add white, black, and gray to pure Add white, black, and gray to pure

pigments to create tints, shades, and tonespigments to create tints, shades, and tones



TintsTints– A pure, fully saturated color combined with whiteA pure, fully saturated color combined with white

ShadeShade– A pure, fully saturated color combined with blackA pure, fully saturated color combined with black

ToneTone– A pure, fully saturated color combined with black A pure, fully saturated color combined with black

and white (gray)and white (gray) Saturation is the amount of white addedSaturation is the amount of white added Value is the amount of black addedValue is the amount of black added Hue is the color that is added toHue is the color that is added to


Overlays and Overlays and TransparencyTransparency

Images are often overlaid on live Images are often overlaid on live video sources at rendering timevideo sources at rendering time– On TV, still images are shown next to On TV, still images are shown next to

live talking heads on the newslive talking heads on the news Normal images are opaqueNormal images are opaque To allow image overlay, some To allow image overlay, some

means must exist to specify means must exist to specify transparency of an image, an image transparency of an image, an image area, or an image pixelarea, or an image pixel



Add overlay bit to image pixel valueAdd overlay bit to image pixel value– When bit is set, rendering application When bit is set, rendering application

ignores those pixel valuesignores those pixel values A rendering application can selectively A rendering application can selectively

toggle overlay bit in all pixel values of toggle overlay bit in all pixel values of a given colora given color– Person standing in front of a contrasting, Person standing in front of a contrasting,

uniformly colored background screen of a uniformly colored background screen of a color which doesn’t appear elsewherecolor which doesn’t appear elsewhere



A rendering application can selectively A rendering application can selectively toggle overlay bit in all pixel values of toggle overlay bit in all pixel values of a given colora given color– Rendering application can toggle overlay Rendering application can toggle overlay

bits of all pixels of this background color, bits of all pixels of this background color, leaving an image of the person cut out leaving an image of the person cut out from the backgroundfrom the background

– This cut-out image can be overlaid on any This cut-out image can be overlaid on any other imageother image

– ChromakeyingChromakeying 256 levels of transparency256 levels of transparency


Bitmap FilesBitmap Files Image data + header informationImage data + header information

– Raw format filesRaw format files Just image dataJust image data

OrganizationOrganization– HeaderHeader

Bitmap dataBitmap data


Bitmap FilesBitmap Files OrganizationOrganization

– HeaderHeaderBitmap dataBitmap dataFooterFooter

– HeaderHeaderPalettePaletteBitmap dataBitmap dataFooterFooter



HeaderHeaderBitmap dataBitmap dataPalettePalette

HeaderHeaderPalettePaletteScan line tableScan line tableColor correction table (here)Color correction table (here)Bitmap dataBitmap dataColor correction table (or here)Color correction table (or here)FooterFooter



– HeaderHeaderPalettePaletteBitmap indexBitmap indexBitmap 1 dataBitmap 1 data……Bitmap N dataBitmap N dataFooterFooter



– HeaderHeaderPalettePaletteBitmap indexBitmap indexPalette 1Palette 1Bitmap 1 dataBitmap 1 dataPalette 2Palette 2Bitmap 2 dataBitmap 2 data……Palette NPalette NBitmap N dataBitmap N dataFooterFooter


Bitmap FilesBitmap Files HeaderHeader

– Binary or ASCII dataBinary or ASCII data– Composed of fixed fieldsComposed of fixed fields– Format of header variesFormat of header varies– Types of fieldsTypes of fields

File identifierFile identifier File versionFile version Number of lines per imageNumber of lines per image Number of pixels per lineNumber of pixels per line


Bitmap FilesBitmap Files HeaderHeader

– Types of fieldsTypes of fields Number of bits per pixelNumber of bits per pixel Number of color planesNumber of color planes Compression typeCompression type X-origin of imageX-origin of image Y-origin of imageY-origin of image Text descriptionText description Unused spaceUnused space


BitmapBitmap HeaderHeader

– File identifierFile identifier Unique identifier which identifies the formatUnique identifier which identifies the format

– GIFGIF– File versionFile version

For GIF, ‘87a’ or ‘89a’For GIF, ‘87a’ or ‘89a’– Number of lines per imageNumber of lines per image

Image lengthImage length Image heightImage height Number of scan linesNumber of scan lines


BitmapBitmap HeaderHeader

– Number of pixels per lineNumber of pixels per line Image widthImage width Scan line widthScan line width

– Number of bits per pixelNumber of bits per pixel Per color planePer color plane Number of bytes per pixel is Number of bytes per pixel is pixel depthpixel depth

– X and Y originsX and Y origins Indicates where image lies on output deviceIndicates where image lies on output device


Color Correction TableColor Correction Table Information to help rendering Information to help rendering

application in displaying an image application in displaying an image on a device different from the one on a device different from the one assumed by the creator applicationassumed by the creator application


Scan-Line TableScan-Line Table An array of offset values used to An array of offset values used to

index the location of each scan lineindex the location of each scan line Each offset value indicates the Each offset value indicates the

starting position of each scan linestarting position of each scan line

Documents

Graphics File Formats