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Perform gamma correction in screenshot.rs #96

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merged 5 commits into from
Feb 8, 2022
Merged

Perform gamma correction in screenshot.rs #96

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e9ced3a
Perform gamma correction in screenshot.rs
LoganDark Jan 25, 2022
23bb581
Merge master
LoganDark Jan 25, 2022
d5011cb
"correct" indentation in screenshot.rs
LoganDark Jan 25, 2022
af82083
(TOTALLY OPTIONAL) use insane rgb565 lookup table
LoganDark Jan 25, 2022
a53e57d
Switch screenshot.rs from embedded LUT to `rgb565` crate
LoganDark Jan 26, 2022
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25 changes: 24 additions & 1 deletion examples/screenshot.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,29 @@ use libremarkable::framebuffer::*;
use libremarkable::image::RgbImage;
use std::fs::OpenOptions;

fn to_srgb([r, g, b]: [u8; 3]) -> [u8; 3] {
// This is a mapping from Linear RGB values to sRGB values, required for output to normal images
// The calculation performed was: ((i as f32 / 255.0).powf(1.0 / 2.2) * 255.0) as u8
const GAMMA: [u8; 256] = [
0, 20, 28, 33, 38, 42, 46, 49, 52, 55, 58, 61, 63, 65, 68, 70, 72, 74, 76, 78, 80, 81, 83,
85, 87, 88, 90, 91, 93, 94, 96, 97, 99, 100, 102, 103, 104, 106, 107, 108, 109, 111, 112,
113, 114, 115, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 128, 129, 130, 131, 132,
133, 134, 135, 136, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 147, 148,
149, 150, 151, 152, 153, 153, 154, 155, 156, 157, 158, 158, 159, 160, 161, 162, 162, 163,
164, 165, 165, 166, 167, 168, 168, 169, 170, 171, 171, 172, 173, 174, 174, 175, 176, 176,
177, 178, 178, 179, 180, 181, 181, 182, 183, 183, 184, 185, 185, 186, 187, 187, 188, 189,
189, 190, 190, 191, 192, 192, 193, 194, 194, 195, 196, 196, 197, 197, 198, 199, 199, 200,
200, 201, 202, 202, 203, 203, 204, 205, 205, 206, 206, 207, 208, 208, 209, 209, 210, 210,
211, 212, 212, 213, 213, 214, 214, 215, 216, 216, 217, 217, 218, 218, 219, 219, 220, 220,
221, 222, 222, 223, 223, 224, 224, 225, 225, 226, 226, 227, 227, 228, 228, 229, 229, 230,
230, 231, 231, 232, 232, 233, 233, 234, 234, 235, 235, 236, 236, 237, 237, 238, 238, 239,
239, 240, 240, 241, 241, 242, 242, 243, 243, 244, 244, 245, 245, 246, 246, 247, 247, 248,
248, 249, 249, 249, 250, 250, 251, 251, 252, 252, 253, 253, 254, 254, 255,
];

[GAMMA[r as usize], GAMMA[g as usize], GAMMA[b as usize]]
}

fn main() {
let fb = Framebuffer::new();
let width = DISPLAYWIDTH as u32;
Expand All @@ -19,7 +42,7 @@ fn main() {
})
.expect("dumping image buffer with known dimensions should succeed")
.chunks_exact(2)
.flat_map(|c| color::NATIVE_COMPONENTS(c[0], c[1]).to_rgb8())
.flat_map(|c| to_srgb(color::NATIVE_COMPONENTS(c[0], c[1]).to_rgb8()))
.collect::<Vec<_>>();

let image =
Expand Down