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Clamp HDR endpoint spread before narrowing it to int #645

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solidpixel merged 1 commit into from
Jun 17, 2026
Merged

Clamp HDR endpoint spread before narrowing it to int #645

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12 changes: 9 additions & 3 deletions Source/astcenc_pick_best_endpoint_format.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -404,9 +404,15 @@ static void compute_color_error_for_every_integer_count_and_quant_level(
// Estimate of color-component spread in low endpoint color
float df = hmax_s(abs(pdif));

int b = static_cast<int>(bf);
int c = static_cast<int>(cf);
int d = static_cast<int>(df);
// Endpoint colors can fall well outside the input range, and an HDR
// input may contain very large or non-finite values, so these spreads
// are not bounded by the int range. Clamp before the narrowing cast to
// avoid undefined behavior; the values are only used in the threshold
// comparisons below and the largest threshold is 32768, so saturating
// at 65536 leaves every comparison result unchanged.
int b = static_cast<int>(astc::clamp(bf, 0.0f, 65536.0f));
int c = static_cast<int>(astc::clamp(cf, 0.0f, 65536.0f));
int d = static_cast<int>(astc::clamp(df, 0.0f, 65536.0f));

// Determine which one of the 6 submodes is likely to be used in case of an RGBO-mode
int rgbo_mode = 5; // 7 bits per component
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