3.16 - Bitmapped Graphics

What is a bitmap image (raster)?

An image built up of pixels.

What is a pixel?

Smallest identifiable area of an image.

How would you represent resolution?

width in pixels x height in pixels

What is meant by PPI?

Pixels Per Inch, this indicates the density of the pixels, rather than the actual image dimensions.

What is meant by DPI?

Dots Per Inch, a printing term relating to the number of ink dots per inch on a page.

What is meant by colour depth?

Number of bits allocated to represent a colour for a pixel.

If an image only has 2 colours, what’s the minimumn colour depth required?

1 bit

What’s the size of a 7×7 pixel image with a colour depth of 2 bits?

1. 7×7=49 (total number of pixels)

2. 49×2 = 98bits

Give examples of metadata for an image.

• Resolution

• Colour Depth

• Date/time taken

• File format

• Creator/author

• Camera/device model

What is mean by metadata?

Data about data.

What are vector images made up of?

Geometric Shapes or objects such as lines, curves arcs and polygons.

How is a vector image different to a bitmapped image?

• Vector images store geometric properties of each shape (coordinates, dimensions, colour, line thickness) as drawing instructions, which are used to redraw the image on load

• Bitmapped images store colour information for every individual pixel

• Vectors can be scaled to any size without losing quality; bitmaps pixelate when enlarged

When is using a bitmapped image preferredover a vector image?

• A vector image can not easily replicate an image with continuous areas of changing colours

• Individual pixels can be manipulated, making bitmaps ideal for photo retouching but vector images allow individual objects to be edited, but individual pixels cannot be directly changed

What is a vector drawing list?

A list of objects/shapes stored within a vector file, each with their own set of properties such as coordinates, dimensions, fill colour, line colour, and line thickness.