ch03 - Chapter 3: Modifying Pictures using Loops 1 Chapter...

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Chapter 3: Modifying Pictures using Loops 1
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Chapter Learning Objectives 2
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We perceive light differently from how it actually is Color is continuous Visible light is in the wavelengths between 370 and 730 nanometers That’s 0.00000037 and 0.00000073 meters But we perceive light with three color sensors that peak around 425 nm (blue), 550 nm (green), and 560 nm (red). Our brain figures out which color is which by figuring out how much of each kind of sensor is responding One implication: We perceive two kinds of “orange” — one that’s spectral and one that’s red+yellow (hits our color sensors just right) Dogs and other simpler animals have only two kinds of sensors They do see color. Just less color. 3
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Luminance vs. Color We perceive borders of things, motion, depth via luminance Luminance is not the amount of light, but our perception of the amount of light. We see blue as “darker” than red, even if same amount of light. Much of our luminance perception is based on comparison to backgrounds, not raw values. Luminance is actually color blind . Completely different part of the brain does luminance vs. color. 4
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Digitizing pictures as bunches of little dots We digitize pictures into lots of little dots Enough dots and it looks like a continuous whole to our eye Our eye has limited resolution Our background/depth acuity is particulary low Each picture element is referred to as a pixel 5
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Pixels Pixels are picture elements Each pixel object knows its color It also knows where it is in its picture When we zoom the picture to 500%, we can see individual pixels. 6
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