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[188.141.3.146]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-432bd0dadcfsm5515322f8f.3.2026.01.06.09.01.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Jan 2026 09:01:15 -0800 (PST) From: Bryan O'Donoghue To: libcamera-devel@lists.libcamera.org Cc: pavel@ucw.cz, Bryan O'Donoghue , Milan Zamazal Subject: [PATCH v11 11/24] libcamera: shaders: Add support for contrast Date: Tue, 6 Jan 2026 17:00:46 +0000 Message-ID: <20260106170059.56193-12-bryan.odonoghue@linaro.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260106170059.56193-1-bryan.odonoghue@linaro.org> References: <20260106170059.56193-1-bryan.odonoghue@linaro.org> MIME-Version: 1.0 X-BeenThere: libcamera-devel@lists.libcamera.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libcamera-devel-bounces@lists.libcamera.org Sender: "libcamera-devel" Apply contrast after black-level and CCM operations. Suggested-by: Milan Zamazal Reviewed-by: Milan Zamazal Signed-off-by: Bryan O'Donoghue --- src/libcamera/shaders/bayer_1x_packed.frag | 19 +++++++++++++++++++ src/libcamera/shaders/bayer_unpacked.frag | 18 ++++++++++++++++++ 2 files changed, 37 insertions(+) diff --git a/src/libcamera/shaders/bayer_1x_packed.frag b/src/libcamera/shaders/bayer_1x_packed.frag index 77d9fbfa7..23747f78a 100644 --- a/src/libcamera/shaders/bayer_1x_packed.frag +++ b/src/libcamera/shaders/bayer_1x_packed.frag @@ -68,6 +68,16 @@ uniform sampler2D tex_y; uniform mat3 ccm; uniform vec3 blacklevel; uniform float gamma; +uniform float contrastExp; + +float apply_contrast(float value) +{ + // Apply simple S-curve + if (value < 0.5) + return 0.5 * pow(value / 0.5, contrastExp); + else + return 1.0 - 0.5 * pow((1.0 - value) / 0.5, contrastExp); +} void main(void) { @@ -261,6 +271,15 @@ void main(void) rgb.g = (rin * ccm[1][0]) + (gin * ccm[1][1]) + (bin * ccm[1][2]); rgb.b = (rin * ccm[2][0]) + (gin * ccm[2][1]) + (bin * ccm[2][2]); + /* + * Contrast + * contrastExp 0..2 contrast to 0..infinity; avoid actual infinity at tan(pi/2) + */ + rgb = clamp(rgb, 0.0, 1.0); + rgb.r = apply_contrast(rgb.r); + rgb.g = apply_contrast(rgb.g); + rgb.b = apply_contrast(rgb.b); + /* Apply gamma after colour correction */ rgb = pow(rgb, vec3(gamma)); diff --git a/src/libcamera/shaders/bayer_unpacked.frag b/src/libcamera/shaders/bayer_unpacked.frag index aba11a87f..af4a30c4b 100644 --- a/src/libcamera/shaders/bayer_unpacked.frag +++ b/src/libcamera/shaders/bayer_unpacked.frag @@ -27,6 +27,16 @@ varying vec4 xCoord; uniform mat3 ccm; uniform vec3 blacklevel; uniform float gamma; +uniform float contrastExp; + +float apply_contrast(float value) +{ + // Apply simple S-curve + if (value < 0.5) + return 0.5 * pow(value / 0.5, contrastExp); + else + return 1.0 - 0.5 * pow((1.0 - value) / 0.5, contrastExp); +} void main(void) { vec3 rgb; @@ -156,6 +166,14 @@ void main(void) { rgb.g = (rin * ccm[1][0]) + (gin * ccm[1][1]) + (bin * ccm[1][2]); rgb.b = (rin * ccm[2][0]) + (gin * ccm[2][1]) + (bin * ccm[2][2]); + /* + * Contrast + */ + rgb = clamp(rgb, 0.0, 1.0); + rgb.r = apply_contrast(rgb.r); + rgb.g = apply_contrast(rgb.g); + rgb.b = apply_contrast(rgb.b); + /* Apply gamma after colour correction */ rgb = pow(rgb, vec3(gamma));