“camera obscura” (“darkened room”)
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CS 148, Summer 2012 Introduction to Computer Graphics and Imaging
Justin Solomon
http://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Motion_interpolation_example.jpg/800px-Motion_interpolation_example.jpg
FINAL
APPROACHING
FINAL
APPROACHING
Makeup? Post on Piazza
http://youtu.be/cKrng7ztpog
http://www.mathworks.com/matlabcentral/fx_files/25653/1/Screen_shot_2009_10_26_at_17.54.20.png
Stack of images
http://www.mathworks.com/matlabcentral/fx_files/25653/1/Screen_shot_2009_10_26_at_17.54.20.png
Stack of images
x y
t
http://www.mathworks.com/matlabcentral/fx_files/25653/1/Screen_shot_2009_10_26_at_17.54.20.png
Stack of images
x y
t
Maintain foreground shape http://en.wikipedia.org/wiki/Seam_carving
http://www.youtube.com/watch?v=3KqiXos1qtw
Find temporally-coherent extensions of image compression
for video.
Find temporally-coherent extensions of image compression
for video.
Codec [koh-dek]:
“Compressor-decompressor;” code for encoding and decoding videos or images.
http://en.wikipedia.org/wiki/Codec
Huge variety of codecs
Different resolution for color http://upload.wikimedia.org/wikipedia/en/0/06/Colorcomp.jpg
Gray plus chroma http://en.wikipedia.org/wiki/YCbCr
Gray plus chroma
Y = 0:299R+ 0:587G+ 0:114B
Cb = 0:564(B ¡ Y ) + 0:5
Cr = 0:713(R¡ Y ) + 0:5
http://voorste.net/tutorials/The.Adobe.Show/Deinterlacing.Video/when.you.get.scaled.interlaced.video.input.jpg
Exploit temporal redundancy http://en.wikipedia.org/wiki/Motion_compensation
Frame
Frame difference
Smaller values!
Exploit temporal redundancy http://en.wikipedia.org/wiki/Motion_compensation
Frame
Frame difference
Smaller values!
Rotate Zoom Translate
code.ucsd.edu/pcosman/253video1.ppt
Frame difference
Compensated difference
Use motion estimate
Divide image into pieces
http://upload.wikimedia.org/wikipedia/commons/b/b1/The_macroblocking_effect_%28JPEG%29.png http://mobileasl.cs.washington.edu/images2/macroblocks.png
Divide image into pieces
http://upload.wikimedia.org/wikipedia/commons/b/b1/The_macroblocking_effect_%28JPEG%29.png http://mobileasl.cs.washington.edu/images2/macroblocks.png
Find source for each target block code.ucsd.edu/pcosman/253video1.ppt
Find source for each target block code.ucsd.edu/pcosman/253video1.ppt
Find source for each target block code.ucsd.edu/pcosman/253video1.ppt
Previous frame
Next frame
Predicted
code.ucsd.edu/pcosman/253video1.ppt
http://www.youtube.com/watch?v=jFqd-7O7r9g
Prevent drift, data loss http://upload.wikimedia.org/wikipedia/commons/6/64/I_P_and_B_frames.svg
I-frame “Intra-coded picture;” full frame
P-frame “Predicted picture;” difference from I-frame (“delta frame”)
B-frame “Bi-predictive picture;” use nearby I-frames
Typical rates:
30 frames per second 2 I-frames per second
10 P-frames per second Remaining frames are B-frames
Moving Picture Experts Group
Typical rates:
30 frames per second 2 I-frames per second
10 P-frames per second Remaining frames are B-frames
Moving Picture Experts Group
DCT Motion Vector
Motion vector with or without DCT of difference;
DCT can be quantized
code.ucsd.edu/pcosman/253video1.ppt
Storing motion vector fields
Representation of motion vectors (precision, generality)
Fourier artifacts
Combinatorics of I/P/B frames
Block size, overlap
Coding depth channel for 3D video
TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAAAAAAAAAA
CS 148, Summer 2012 Introduction to Computer Graphics and Imaging
Justin Solomon
http://graphics.stanford.edu/courses/cs178-11/
“Camera Obscura” (“Darkened Room”) http://graphics.stanford.edu/courses/cs178/lectures/image-formation-03apr12.pdf
“Camera Obscura” (“Darkened Room”) http://graphics.stanford.edu/courses/cs178/lectures/image-formation-03apr12.pdf
“Camera Obscura” (“Darkened Room”) http://graphics.stanford.edu/courses/cs178/lectures/image-formation-03apr12.pdf
Ray tracing image plane
“Camera Obscura” (“Darkened Room”) http://graphics.stanford.edu/courses/cs178/lectures/image-formation-03apr12.pdf
Ray tracing image plane
One ray of light is not very much.
Fuzzy superposition of images http://www.schoolphysics.co.uk/age11-14/Light/experiments/pinhole_camera/index.html
1
S1+
1
S2=
1
fhttp://en.wikipedia.org/wiki/Lens_%28optics%29
1
S1+
1
S2=
1
fhttp://en.wikipedia.org/wiki/Lens_%28optics%29
http://upload.wikimedia.org/wikipedia/commons/9/92/Spherical_aberration_2.svg
Spherical aberration
http://upload.wikimedia.org/wikipedia/commons/9/92/Spherical_aberration_2.svg
Chromatic aberration
http://graphics.stanford.edu/courses/cs148-11-fall/lectures/camera.pdf
http://graphics.stanford.edu/courses/cs148-10-summer/docs/03_cam_disp_cmpr.pdf
Range of angles captured by sensor
Wide angle lens Telephoto lens
Amount of light reaching sensor
Shutter speed Aperture
http://graphics.stanford.edu/courses/cs148-10-summer/docs/03_cam_disp_cmpr.pdf
Resolution [rez-uh-loo-shuhn]:
Number of pixels in a digital image.
Pixel pitch [pik-suhl pich]:
Density of pixels on a sensor or display.
Maximize contrast Measured in terms of gradients
Phase detection Compare multiple images that should align
http://upload.wikimedia.org/wikipedia/commons/5/5a/Autofocus_phase_detection.svg
Charge-Coupled Device (CCD)
Complementary Metal-Oxide-Semiconductor
(CMOS) http://en.wikipedia.org/wiki/Charge-coupled_device http://cpn.canon-europe.com/files/education/infobank/capturing_the_image/cmos.jpg
Digital cameras have processors that can do simple image processing
before storage.
Color filter array (CFA) http://en.wikipedia.org/wiki/Bayer_filter
Combined M and L cones
during day are most sensitive
to green
Undo Bayer filter pattern http://upload.wikimedia.org/wikipedia/commons/e/e1/Shades_framed_bayer.png
Interpolation (linear or otherwise)
Interpolation (linear or otherwise)
displayed intensity = (maximum intensity)a°
http://www.kenluckephotography.com/portfolio/monitoradjust/files/page17_2.gif
http://upload.wikimedia.org/wikipedia/commons/b/be/Photo_editing_contrast_correction.jpg
http://upload.wikimedia.org/wikipedia/commons/b/be/Photo_editing_contrast_correction.jpg
Looks like a gamma curve!
Histogram equalization http://en.wikipedia.org/wiki/Histogram_equalization
Brighter dark
regions
http://gfoto.tripod.com/phototips/phototips/noise.jpg
http://generalspecialist.com/greenscreen-and-bluescreen-checklist/
I 7! I ¤G+¯(I ¡ I ¤G)
http://www.fotoview.nl/images/usm.jpg http://www.digiretus.com/tippek/photoshop02/sample.jpg
Joint File Interchange Format
1.Optionally convert color spaces 2.Reduce chroma data (usually by 2x) 3.Apply discrete cosine transform to
8x8 blocks 4.Quantize DCT values 5.Store result using lossless encoding
Joint File Interchange Format
1.Optionally convert color spaces 2.Reduce chroma data (usually by 2x) 3.Apply discrete cosine transform to
8x8 blocks 4.Quantize DCT values 5.Store result using lossless encoding
Exchangeable Image File Format
Image format that stores lots of metadata
http://upload.wikimedia.org/wikipedia/commons/6/6a/Konqueror_Exif_data.jpg
“Digital negative”
Store sensor data directly
http://community.futureshop.ca/t5/Tech-Blog/Urban-legends-the-RAW-format/ba-p/155011
RAW JPEG Overexposed
Lots of data to store or process http://ak.buy.com/PI/0/500/232992343.jpg
“Frankencamera” http://graphics.stanford.edu/projects/camera-2.0/images/frankencamera-2.0-2-sshbal.jpg
http://research.microsoft.com/en-us/um/redmond/projects/flashnoflash/flash_no_flash%20%28web%29.pdf
http://upload.wikimedia.org/wikipedia/en/5/53/Image_pipeline2.png
TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAAAAAAAAAA
CS 148, Summer 2012 Introduction to Computer Graphics and Imaging
Justin Solomon
http://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Motion_interpolation_example.jpg/800px-Motion_interpolation_example.jpg http://graphics.stanford.edu/courses/cs178-11/
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