Bitmap Graphics Graphics

Graphics L2 Bitmap Graphics Learning Objectives Understand how a bitmap graphic is made up of individual pixels Understand that the number of bits per pixel determines the number of available colours for an image Compare the different characteristics, strengths and uses of vector and bitmap images Manipulate vector and bitmap images

Graphics L2 Bitmap Graphics What are Bitmap graphics? A Bitmap graphic is also known as a Raster graphic A bitmap graphic is composed of tiny squares, called pixels It is possible to edit each individual pixel. The computer stores information about the colour value of every pixel in the image. This can mean a large file size Resizing a Bitmap graphic causes it to pixelate and lose quality

Graphics L2 Bitmap Graphics Representing Graphics Images are made up of Pixels (Picture Elements) Each pixel is set to one colour Together they look like an image Pixels small enough are unidentifiable

Graphics L2 Bitmap Graphics Using Picture Elements for an Image Not a new idea to use small squares of colour The ancient Romans created mosaics

Graphics L2 Bitmap Graphics Modern Picture Elements Structured in a Grid Each pixel is given a numeric value Each value represents one colour

Graphics L2 Bitmap Graphics Creating an Image Each Pixel is given a binary value Each value represents a different colour Using one bit per pixel allows only 2 values, 0 and 1 1 = White, 0 = Black

Graphics L2 Bitmap Graphics Creating an Image More bits per pixel = more colour combinations – 1 bit = 2 Colours – 2 bits = 4 Colours – 3 bits = 8 Colours – 4 bits = 16 Colours How many bits per pixel required for 256 colours? =11 = 01 =10 =

Graphics L2 Bitmap Graphics Bits and Bytes 0 or a 1=1 Bit (Binary Digit) 8 Bits=1 Byte 1024 Bytes=1 Kilobyte (Kb) 1024 Kb=1 Megabyte (Mb) 1024 Mb =1 Gigabyte (Gb)

Graphics L2 Bitmap Graphics Colours vs File Size How many bits in this picture? What if each pixel was one of 256 colours? How does the number of colours affect file size?

Graphics L2 Bitmap Graphics Bitmap images are used for... Digital camera images Scanned Images Magazine covers Photographs

Graphics L2 Bitmap Graphics Natural porcelain skin? Photo-editing can manipulate individual pixels using a Bitmap file format such as.jpg or.png

Graphics L2 Bitmap Graphics How a camera ‘sees’ an image Each tiny square on the sensor captures the average light value of the colours it ‘sees’ This is interpreted as a colour and becomes a pixel of solid colour

Graphics L2 Bitmap Graphics Bitmap or Vector graphic? Will the image need to be resized? Will the image need to be drawn to scale? Will the image need to be realistic? Are there any restrictions on file size?

Graphics L2 Bitmap Graphics Simple Vector Art Comprises 2D or 3D geometric shapes

Graphics L2 Bitmap Graphics Exploding a vector image Ungroup the shapes You can isolate individual elements and change their properties

Graphics L2 Bitmap Graphics Pixelation

Graphics L2 Bitmap Graphics Comparing Bitmap graphicsVector graphics Made up ofColoured pixelsObjects File sizeLargeSmall ResizingLose qualityNo loss of quality AppearanceRealCartoon-like File formats.bmp.jpg.gif.svg.wmf