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Transferring Color to Greyscale Images

Transferring Color to Greyscale Images. Tomihisa Welsh, Michael Ashikhmin, Klaus Mueller (Stony Brook University) SIGGRAPH2002. What is Colorization?. Woody Allen:

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Transferring Color to Greyscale Images

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  1. Transferring Color to Greyscale Images Tomihisa Welsh, Michael Ashikhmin, Klaus Mueller (Stony Brook University) SIGGRAPH2002

  2. What is Colorization? • Woody Allen: • "colorization" of films "is a `monstrous,' disgusting,' horrible,' `sinful,' `absurd,' `humiliating,' `preposterous,' and `insulting' mutilation and defacing of genuine works of art, in which computers are used to `doctor' and `tamper' with the `great originals,' thereby creating `degraded,' `cheesy,' artificial symbols of one society's greed."

  3. What can it do? • “Colorize” old movies • Make black and white pictures color • Adds a dimension to MRI’s or airport luggage scans • Lifelike electron microscope scans

  4. Why is it difficult? • Grayscale images consist of one dimensional data • Luminance data • No Saturation or Hue • 3D HSL colors have 256x256 or ~66,000 colors with a given Luminance

  5. It’s still not easy… • Different sections of an image might have same lumination but very different hue.

  6. But let’s give it a shot • We need a color space • HSL and RGB just wont cut it • Domo Arigato Mr. Ruderman et. Al. 1998 • Created l, a, B color space • Decorellated space • Linearly independent • Luminance ( l ) • Yellow-blue ( a ) • Red-Green ( B )

  7. Come again? • Conversion: • LMS = Long, medium, and short wavelength • Now that we have our new color space, we turn to some sadis…I mean statistics

  8. Scale and correct l, a, and B

  9. RGB to LAB

  10. Luminance Mapping • Source image = color image • Target image = grayscale image

  11. Luminance Mapping part Deux • Hertzmann et. Al. 2001 • Standard deviation of 5x5 pixel neighborhood • Match source and target based on combination of luminance (50%) and std. dev. (50%) • Map the match

  12. Map it Source Luminance Channel Target Remapped

  13. Houston… • There is a problem with this. • What if there are different sections of the picture?

  14. Swatches • Indicate similar parts of a scene

  15. Examples

  16. More Examples

  17. Video • Why not extend this to video? • Industry born in 1970 (Wilson Markle) • Recolorized movies use these techniques • Source frame used every camera change • Once have first target, use that as source • User-defined swatches can track movement

  18. Waves

  19. Horses

  20. This is your brain

  21. At what cost? • In 1987 $3,000/min or $300,000/movie • One Critic calls it the “Bastardization” of film • Brings in on average $500,000/release

  22. Oh, Cool

  23. Wrap-Up • Get source and target • Convert colors to l, a, B • Map colors • Use swatches for faster better results • Process takes between 15 seconds and 4 minutes on Pentium III 900 MHz CPU • Use MATLAB

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