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gamma_correction
/* gamma_correction
*
* By: Andrew Tuline
*
* Date: January, 2019
*
* Testing gamma correction to change LED brightness so that it appears to change evenly for the viewer. The problem is that changes above
* 50 are much less noticeable for the viewer, so the LED gets bright quickly and then stays bright for way too long before dimming again.
*
* There's a few ways to adjust LED output. The table method was proposed on Adafruit.com. Here's a couple of other methods for demonstration.
*
* Display the result on the Arduino IDE's serial plotter.
*
*
* Resources:
*
* Gamma correction: https://learn.adafruit.com/led-tricks-gamma-correction/the-issue
*
* fscale.h: http://playground.arduino.cc/main/fscale
*
*/
#include "FastLED.h" // This is required for some of the math routines.
const uint8_t PROGMEM gamma8[] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2,
2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5,
5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10,
10, 10, 11, 11, 11, 12, 12, 13, 13, 13, 14, 14, 15, 15, 16, 16,
17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 24, 24, 25,
25, 26, 27, 27, 28, 29, 29, 30, 31, 32, 32, 33, 34, 35, 35, 36,
37, 38, 39, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 50,
51, 52, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68,
69, 70, 72, 73, 74, 75, 77, 78, 79, 81, 82, 83, 85, 86, 87, 89,
90, 92, 93, 95, 96, 98, 99,101,102,104,105,107,109,110,112,114,
115,117,119,120,122,124,126,127,129,131,133,135,137,138,140,142,
144,146,148,150,152,154,156,158,160,162,164,167,169,171,173,175,
177,180,182,184,186,189,191,193,196,198,200,203,205,208,210,213,
215,218,220,223,225,228,231,233,236,239,241,244,247,249,252,255 };
void setup() {
Serial.begin(57600);
} // setup()
void loop() {
for (int i = 0; i<512; i++) {
Serial.print(0); Serial.print(" "); Serial.print(255); Serial.print(" "); // Use this to fix the scaling.
uint8_t inputval = sin8(i); // Good enough for graphing.
Serial.print(inputval);
uint8_t results = pgm_read_byte(&gamma8[inputval]); // That sinewave is now corrected via the lookup table, which is quick, but consumes flash.
Serial.print(" "); Serial.print(results);
uint8_t dimraw = dim8_raw(inputval); // The FastLED dim8_raw routine doesn't work as well as the table.
Serial.print(" "); Serial.print(dimraw);
uint8_t newval = inputval*inputval/255; // A non-floating point exponential multiplier is close to the table, but a bit slow.
newval = newval*inputval/255;
Serial.print(" "); Serial.print(newval);
float num = pow((inputval/255.0), 3.0); // The floating point exponential multiplier is adjustable, but slow.
int n = num * 255;
Serial.print(" "); Serial.print(n);
Serial.println(" ");
}
while(1); // We're going to stop right here!
} // loop()
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