Gamma

Most LCD Controllers has a way to adjust the brightness of the colours. This is to match LCD panels with different characteristics.

Some controllers have one table/curve and other have one positive and one negative.

Some FBTFT drivers has support for configurable gamma correction. The table/curve can be set with the gamma argument of fbtft_device or through /sys/class/graphics/fb1/gamma.

Format: Each value is separated by space or comma. Each row/curve is separated by semicolon or newline.

Examples

sudo modprobe fbtft_device name=ssd1351fb gamma=5,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,1,1,1,2,2,2,2,2,3,3,3,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5

/bin/echo "5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 1 1 1 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5 5 5 5" > /sys/class/graphics/fb1/gamma

itdb28fb (ILI9325)

Default gamma

0F,00,7,2,0,0,6,5,4,1;04,16,2,7,6,3,2,1,7,7

ssd1351fb (SSD1351)

This controller has 1 Grayscale Lookup Table. Ref. 10.1.16 Look Up Table for Gray Scale Pulse width (B8h)

Default gamma

5,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,1,1,1,2,2,2,2,2,3,3,3,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5