lecture8 - CSE 471 Media Processing and Multimedia...

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1 CSE 471 Media Processing and Multimedia Introduction to Digital Images Representations of samples in images Raster images Monochrome Color
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2 CSE 471 Media Processing and Multimedia Capture of Sampled Images Grid of light sensors
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3 CSE 471 Media Processing and Multimedia Light Sensors Sample and Hold Analog to Digital Digital value for the sensor Takes a measurement and “holds” it for conversion to digital. Converts a measurement to digital
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4 CSE 471 Media Processing and Multimedia Pixels Pixel – picture element Pixels Binary pixels – 1 or 0 – Bitmap images Planes – the number of color components Gray scale images – 1 plane Pixel values range from MIN to MAX Typically 0 to 255 (but, 12 and 16 bit not uncommon) Color images – 3 planes Typically Red, Green, Blue (RGB) 8 bits
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5 CSE 471 Media Processing and Multimedia Integer Representations Integers are most common: 8 bit = 256 “steps” 16 bit = 65536 steps Digital Audio Usually 16 bits Represent using short Digital Images Usually 8 bits Represent using unsigned char typedef unsigned char BYTE;
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6 CSE 471 Media Processing and Multimedia Alpha maps Also common: 4 planes, where one is an alpha map Value indicates the transparency of the pixel 0 = opaque, 255 = completely seethrough Common for overlays, bugs, fog, computer graphics Often referred to as RGBA
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7 CSE 471 Media Processing and Multimedia Pitfalls BGR almost as common as RGB RGBA is very common even if we don’t use the A component (why?) Bitmaps may be stored 1 pixel per BYTE or 8 pixel per BYTE
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8 CSE 471 Media Processing and Multimedia Bitmap images (Thresholding)
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CSE 471 Media Processing and Multimedia Bitmap representations Common means of representation (in memory) – 8 pixels per byte int usewid = (WIDTH + 7) / 8; // Ceiling 1-8 -> 1 9-16 -> 2 etc. // If you know for sure…
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lecture8 - CSE 471 Media Processing and Multimedia...

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