Reads and performs color transform a Windows BMP
Code Fellows 401 JS assignment by Natalie Chow, Yueyue Qin, and Sabrina Tee
The transformer can be called from the command line with the following format:
node index.js <file_path> [<transform>[=<parameter>]]
<file_path> points to the bitmap file relative to the root directory.
The optional <transform> can be used to specify a single color transform method. If no <transform> argument is passed, the default transformation of inverse will be used. Some <transform> takes a <parameter>, which is also optional. See below for a list of methods and their details of implementation.
To see a list of color transform methods available, type in the command line:
node index.js help
Our code is written to handle decoding on both LE and BE machines.
Our color transform methods work on both paletted and non-paletted bitmaps, specifically 8-bit indexed colors, as well as 24-bit (RGB) and 32-bit (RGBA) non-paletted color depths. The alpha value in 32-bit color will not be modified to retain the original transparency.
inverse is the default transform. It flips each of the RGB value on the spectrum such that (R, G, B) becomes (255 - R, 255 - G, 255 - B).
These colorscales work the same way - for each pixel, a specific color value (R/G/B) is multiplied by a constant. If the multiplied value exceeds 255, the fractional value is used. The multiplier is defaulted to be 2, but can be customized by passing it as a parameter:
node index.js img/mario.bmp bluescale=4.3
The addredscale, addgreenscale, addbluescale series adds a constant value defined by the user in the command line. If no value is passed, the default is set to 10.
node index.js img/mario.bmp addredscale=20
The average grayscale, as suggested by its name, averages the RGB value at each pixel and replaces each with (R + G + B) / 3.
The lightness transform takes the average of the most and least prominent colors. The RGB values are then assigned to be (max + min) / 2 where max = max(R, G, B) and min = min(R, G, B).
luminosity uses a weighted average to account for human perception. Green is given a large proportion because we are more sensitive to green light. The RGB value is calculated to be 0.2125R + 0.7154G + 0.0721B
scatterbrain randomizes each RGB value.
sepiaish makes the image a bit browner? Who even knows. Try it.
noise adds a fixed random value to each RGB value, to add some noise to the image.