topic about gamma correction in i.MX Processors

about gamma correction

linzhang — Tue, 16 Jan 2018 11:26:25 GMT

I wan't to implement a display contrast adjustment machanism in linear mode, but I don't know how to do it.

according to Gamma correction on i.MX6 , following steps can do gamma correction:

1 - Declare a variable as mxcfb_gamma:

struct mxcfb_gamma fb_gamma;

2 - Enable the gama correction:

fb_gamma.enable = 1;

3 - Set the constk and slopek values, where i = 0 to 15 and x and y are respectively the new constk and slopek constant values:

fb_gamma.constk[i] = x;

fb_gamma.slopek[i] = y;

4 - Open the framebuffer device and call MXCFB_SET_GAMMA:

fd_fb = open("/dev/fb0", O_RDWR, 0)

ioctl(fd_fb, MXCFB_SET_GAMMA, &fb_gamma)

how do I choose the constk & slopek values to insure the contrast vary in linear mode?

Re: about gamma correction

b36401 — Thu, 18 Jan 2018 06:24:44 GMT

For linear transfer function you can simply turn off gamma correction.

Have a great day,
Victor

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Re: about gamma correction

linzhang — Thu, 18 Jan 2018 11:20:39 GMT

how to turn off gamma correction?

after turning off, how to adjust display's contrast in linear way?

Can you show me some example codes?