Imaging Flashcards
Brightness or color=
G(x,y) or f(row,column)
For a certain instance of time
Image recovers reflections
Object reflects light to camera> Sensor element receives light energy Intensity matters Angles matter Materials matter
Factors that affect light perception
Light, reflectance, specularity (shiny), distance, angles, sensor sensitivity
Pinhole camera
Captures pencils of rays to focus image. Since only some rays are caught, it reduces blurring
Past techniques of image making
Camera obscura ( Darkened room with pinhole camera)
19th cent- lens and light sensitive paper
20th cent- electric light sensor
Pinhole diameter is the
Aperture, this affects how much light gets in which blur the images of too small (diffraction)or too big
Modeling projection coordinate system
Images are flipped when projected
O = optical center at origin X,y = image plane coordinates Z = optical axis
Projections are derived using similar triangles
Objects that are projected from a farther distance are perceived…
Smaller than those that are close
Geometric properties of perspective projection
Points in 3D point to points in 2D
So do lines
Angles and distances aren’t preserved
Parallel lines project to parallel lines only if they are parallel to image plane
Vanishing point
Where parallel lines converge
An extra coordinate (homogeneous coordinates)
An extra coordinate that represent scale
x, y, 1
Weak perspective
Aka scaled orthography
NEED MORE INFO
Orthographic perspective
NEED MORE INFO
Camera parameters- coordinate systems
Camera coordinate system
World coordinate system
Camera intrinsics
Project world coordinate (x,y,z) to camera coordinates then project onto an image plane to get an image coordinate
Camera parameters - features
Extrinsics: Translation T of O from world origin Rotation R of image plane Intrinsics: Focal length F Principle point Pixel size
Photoreceptors
Rods (luminence)
Cones (color) (RGB)
