go-mxl-pattern-generator/kernels/static/smpteBars.wgsl

// SMPTE RP 219-1 Color Bar Pattern Generator
// 10-bit Y'CbCr packed as v210 (4:2:2). Compliant with SMPTE RP 219-1:2014

struct Params {
    width: u32,
    height: u32,
    frame: u32,
    _pad0: u32,
};

@group(0) @binding(0) var<storage, read_write> out: array<u32>;
@group(0) @binding(1) var<uniform> params: Params;

fn bar_index(px: u32, bars_75_width: u32) -> u32 {
    return min((px * 7u) / bars_75_width, 6u);
}

@compute @workgroup_size(64)
fn main(@builtin(global_invocation_id) gid: vec3<u32>) {
    let block = gid.x;
    let total = (params.width * params.height) / 6u;
    if (block >= total) {
        return;
    }

    let x = (block * 6u) % params.width;
    let y_px = (block * 6u) / params.width;

    // 75% Color Table: white, yellow, cyan, green, magenta, red, blue
    let y_tab  = array<u32, 7>(721u, 674u, 581u, 534u, 251u, 204u, 111u);
    let cb_tab = array<u32, 7>(512u, 176u, 589u, 253u, 771u, 435u, 848u);
    let cr_tab = array<u32, 7>(512u, 543u, 176u, 207u, 817u, 848u, 481u);

    // Layout calculations mapping the 4:3 area centered in a 16:9 canvas
    let bars_width: u32 = (params.height / 3u) * 4u;
    let bars_start: u32 = (params.width - bars_width) / 2u;
    let bars_end: u32 = bars_width + bars_start;
    let one_bar_width: u32 = bars_width / 7u;

    // Strict vertical boundary calculations based on 12th parts
    let unit_h: u32 = params.height / 12u;
    let bound_s1: u32 = unit_h * 7u;          // Row 630 on 1080p
    let bound_s2: u32 = bound_s1 + unit_h;    // Row 720 on 1080p
    let bound_s3: u32 = bound_s2 + unit_h;    // Row 810 on 1080p

    // Section 3 Linear Y-Ramp boundaries
    let ramp_start = bars_start + one_bar_width;
    let ramp_end = bars_end;
    let ramp_width = ramp_end - ramp_start;

    var y: array<u32, 6>;
    var cb: array<u32, 6>;
    var cr: array<u32, 6>;

    for (var i = 0u; i < 6u; i++) {
        let px_x = x + i;

        // SECTION 1 (Top 7/12): Main 75% Color Bars
        if (y_px < bound_s1) {
            if (px_x >= bars_start && px_x < bars_end) {
                let b = bar_index(px_x - bars_start, bars_width);
                y[i] = y_tab[b];
                cb[i] = cb_tab[b];
                cr[i] = cr_tab[b];
            } else {
                // 40% Gray Flanks
                y[i] = 414u; cb[i] = 512u; cr[i] = 512u;
            }
        }
        // SECTION 2 (Next 1/12): 100% Cyan, -I Signal, 75% White, 100% Blue
        else if (y_px >= bound_s1 && y_px < bound_s2) {
            if (px_x < bars_start) {
                y[i] = 754u; cb[i] = 615u; cr[i] = 64u;   // 100% Cyan
            } else if (px_x >= bars_start && px_x < ramp_start) {
                y[i] = 244u; cb[i] = 612u; cr[i] = 395u;  // -I Signal
            } else if (px_x >= bars_end) {
                y[i] = 127u; cb[i] = 960u; cr[i] = 471u;  // 100% Blue
            } else {
                y[i] = 721u; cb[i] = 512u; cr[i] = 512u;  // 75% White
            }
        }
        // SECTION 3 (Next 1/12): 100% Yellow, +Q Signal, Linear Y-Ramp, 75% Red
        else if (y_px >= bound_s2 && y_px < bound_s3) {
            if (px_x < bars_start) {
                y[i] = 877u; cb[i] = 64u;  cr[i] = 553u;  // 100% Yellow
            } else if (px_x >= bars_start && px_x < ramp_start) {
                y[i] = 141u; cb[i] = 697u; cr[i] = 606u;  // +Q Signal
            } else if (px_x >= bars_end) {
                y[i] = 250u; cb[i] = 409u; cr[i] = 960u;  // 75% Red
            } else {
                // Perfect linear scaling from Digital Black (64u) to Digital White (940u)
                let clamped_x = clamp(px_x, ramp_start, ramp_end);
                y[i] = 64u + ((clamped_x - ramp_start) * (940u - 64u)) / ramp_width;
                cb[i] = 512u;
                cr[i] = 512u;
            }
        }
        // SECTION 4 (Bottom 3/12): Pluge Panel Calibration Blocks
        else {
            if (px_x >= bars_start && px_x < bars_end) {
                let b = (px_x - bars_start) / one_bar_width;

                if (b == 0u || b == 2u || b >= 4u) {
                    y[i] = 64u; cb[i] = 512u; cr[i] = 512u;   // 0% Black
                } else if (b == 1u) {
                    y[i] = 940u; cb[i] = 512u; cr[i] = 512u;  // 100% White Calibration
                } else if (b == 3u) {
                    // PLUGE Sub-bar generation (Split into 3 absolute equal fragments)
                    let sub_bar_offset = (px_x - bars_start) % one_bar_width;
                    let sub_b = (sub_bar_offset * 3u) / one_bar_width;

                    cb[i] = 512u;
                    cr[i] = 512u;
                    if (sub_b == 0u) {
                        y[i] = 46u;  // -2% Sub-Black
                    } else if (sub_b == 1u) {
                        y[i] = 64u;  // 0% Black
                    } else {
                        y[i] = 82u;  // +2% Above-Black
                    }
                }
            } else {
                // 15% Gray Flanks
                y[i] = 195u; cb[i] = 512u; cr[i] = 512u;
            }
        }
    }

    // Packing into standard v210 10-bit macroblock layout words
    out[block * 4u + 0u] = (cb[0] & 0x3FFu) | ((y[0] & 0x3FFu) << 10u) | ((cr[0] & 0x3FFu) << 20u);
    out[block * 4u + 1u] = (y[1] & 0x3FFu) | ((cb[2] & 0x3FFu) << 10u) | ((y[2] & 0x3FFu) << 20u);
    out[block * 4u + 2u] = (cr[2] & 0x3FFu) | ((y[3] & 0x3FFu) << 10u) | ((cb[4] & 0x3FFu) << 20u);
    out[block * 4u + 3u] = (y[4] & 0x3FFu) | ((cr[4] & 0x3FFu) << 10u) | ((y[5] & 0x3FFu) << 20u);
}