From 248241b6e18ecf0d9cb2706419952ae933ad78d8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Erik=20Pedersen?=
 <bjorn.erik.pedersen@gmail.com>
Date: Thu, 4 Jun 2026 14:42:08 +0200
Subject: [PATCH] Cap AVIF lossy quality at 99

Before this commit, lossy compression with 100 quality meant lossless compression, leading to a big gap between 99 and 100.

This commit caps the lossy quality at 99, ensuring that lossy compression is always lossy.

Fixes #14981
---
 internal/warpc/genavif/avif.c |   4 ++++
 internal/warpc/wasm/avif.wasm | Bin 7271421 -> 7271445 bytes
 2 files changed, 4 insertions(+)

diff --git a/internal/warpc/genavif/avif.c b/internal/warpc/genavif/avif.c
index f572f7cf5..3932f7fcb 100644
--- a/internal/warpc/genavif/avif.c
+++ b/internal/warpc/genavif/avif.c
@@ -685,6 +685,8 @@ void handle_commands(FILE *stream)
                 if (quality < 1) quality = 1;
                 if (quality > 100) quality = 100;
                 int avif_quality = (int)((quality - 1.0) / 99.0 * 100.0);
+                // Keep lossy strictly below lossless so quality 100 stays lossy. See issue 14981.
+                if (avif_quality >= AVIF_QUALITY_LOSSLESS) avif_quality = AVIF_QUALITY_LOSSLESS - 1;
                 encoder->quality = avif_quality;
                 encoder->qualityAlpha = avif_quality;
             }
@@ -809,6 +811,8 @@ void handle_commands(FILE *stream)
                 if (quality < 1) quality = 1;
                 if (quality > 100) quality = 100;
                 int avif_quality = (int)((quality - 1.0) / 99.0 * 100.0);
+                // Keep lossy strictly below lossless so quality 100 stays lossy. See issue 14981.
+                if (avif_quality >= AVIF_QUALITY_LOSSLESS) avif_quality = AVIF_QUALITY_LOSSLESS - 1;
                 encoder->quality = avif_quality;
             }
             encoder->qualityAlpha = AVIF_QUALITY_LOSSLESS;
diff --git a/internal/warpc/wasm/avif.wasm b/internal/warpc/wasm/avif.wasm
index 4fb7b29956d77de752627a2d31845da7a3f5e36d..9968def00da555070ab9c282743b1e8ba3c84e67 100755
GIT binary patch
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