xypath_renderer.cpp

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#include <math.h>
 
#include "fl/assert.h"
#include "fl/warn.h"
#include "fl/xypath.h"
#include "fl/xypath_renderer.h"
 
namespace fl {
 
namespace {
uint8_t to_uint8(float f) {
    // convert to [0..255] range
    uint8_t i = static_cast<uint8_t>(f * 255.0f + .5f);
    return MIN(i, 255);
}
} // namespace
 
XYPathRenderer::XYPathRenderer(XYPathGeneratorPtr path,
                               TransformFloat transform)
    : mPath(path), mTransform(transform) {}
 
vec2f XYPathRenderer::compute_float(float alpha, const TransformFloat &tx) {
    vec2f xy = mPath->compute(alpha);
    vec2f out = tx.transform(xy);
    out = mGridTransform.transform(out);
    return out;
}
 
Tile2x2_u8 XYPathRenderer::at_subpixel(float alpha) {
    // 1) continuous point, in “pixel‐centers” coordinates [0.5 … W–0.5]
    if (!mDrawBoundsSet) {
        FASTLED_WARN("XYPathRenderer::at_subpixel: draw bounds not set");
        return Tile2x2_u8();
    }
    vec2f xy = at(alpha);
 
    // 2) shift back so whole‐pixels go 0…W–1, 0…H–1
    float x = xy.x - 0.5f;
    float y = xy.y - 0.5f;
 
    // 3) integer cell indices
    int cx = static_cast<int>(floorf(x));
    int cy = static_cast<int>(floorf(y));
 
    // 4) fractional offsets in [0..1)
    float fx = x - cx;
    float fy = y - cy;
 
    // 5) bilinear weights
    float w_ll = (1 - fx) * (1 - fy); // lower‑left
    float w_lr = fx * (1 - fy);       // lower‑right
    float w_ul = (1 - fx) * fy;       // upper‑left
    float w_ur = fx * fy;             // upper‑right
 
    // 6) build Tile2x2_u8 anchored at (cx,cy)
    Tile2x2_u8 out(vec2<int>(cx, cy));
    out.lower_left() = to_uint8(w_ll);
    out.lower_right() = to_uint8(w_lr);
    out.upper_left() = to_uint8(w_ul);
    out.upper_right() = to_uint8(w_ur);
 
    return out;
}
 
} // namespace fl