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Understanding Images: A Journey from Camera Obscura to Digital Pixels

Explore the evolution of image capture, starting from ancient Chinese camera obscura to the cutting-edge digital cameras of the late 20th century. Delve into the mechanics of images as 2D arrays of pixels governed by the RGB color model. Understand key concepts like sampling, reconstruction, brightness adjustment, and contrast scaling, as well as advanced techniques such as image warping and morphing. This comprehensive overview provides a foundational knowledge of how images are created, manipulated, and represented in today’s digital format.

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Understanding Images: A Journey from Camera Obscura to Digital Pixels

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Presentation Transcript

  1. Part 1: ImagesQ: What is an image?

  2. Brief history of image capture • Camera obscura • Known to Chinese 5thC. BC • 19th century: Camera • Hole  Lens • Paper  Light sensitive • Late 20th century: Digital camera • Light-senstive paper  CCD/electronics

  3. Digital images • Rectangular (2D) array of pixels Continuous image Digital image

  4. RGB Color Model R G B Color 0.0 0.0 0.0 Black 1.0 0.0 0.0 Red 0.0 1.0 0.0 Green 0.0 0.0 1.0 Blue 1.0 1.0 0.0 Yellow 1.0 0.0 1.0 Magenta 0.0 1.0 1.0 Cyan 1.0 1.0 1.0 White 0.5 0.0 0.0 ? 1.0 0.5 0.5 ? 1.0 0.5 0.0 ? 0.5 0.3 0.1 ? Colors are additive Plate II.3 from FvDFH

  5. What is an Image? • Rectangular (2D) array of pixels Continuous image Digital image

  6. What is an Image? (digital audio) • Rectangular (2D) array of pixels A pixel is a sample, not a little square! Continuous image Digital image

  7. Sampling and Reconstruction Sampling(e.g. digital camera) Reconstruction(e.g. CRT)

  8. Adjusting Brightness • Simply scale pixel components • Must clamp to range (e.g., 0 to 1) Original Brighter

  9. Adjusting Contrast • Compute average luminance L for all pixels • L = 0.30*r + 0.59*g + 0.11*b • Scale deviation from L for each pixel • Must clamp to range (e.g., 0 to 1) L Original More Contrast

  10. Scaling the image • Resample withfewer or more pixels(mathy theory…) Original 1/4X resolution 4X resolution

  11. Warp Source image Destination image Image Warping • Move pixels of image (resampling)

  12. Image Morphing [Beier & Neeley] Image0 Warp0 Result Image1 Warp1

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