[{"id":37252,"web_url":"https://patchwork.libcamera.org/comment/37252/","msgid":"<854ipy5sfz.fsf@mzamazal-thinkpadp1gen7.tpbc.csb>","date":"2025-12-10T14:20:48","subject":"Re: [PATCH v7 10/26] libcamera: shaders: Add support for contrast","submitter":{"id":177,"url":"https://patchwork.libcamera.org/api/people/177/","name":"Milan Zamazal","email":"mzamazal@redhat.com"},"content":"Bryan O'Donoghue writes:\n\n> Apply contrast after black-level and CCM operations.\n>\n> Suggested-by: Milan Zamazal \n> Signed-off-by: Bryan O'Donoghue \n> ---\n> src/libcamera/shaders/bayer_1x_packed.frag | 19 +++++++++++++++++++\n> src/libcamera/shaders/bayer_unpacked.frag | 19 +++++++++++++++++++\n> 2 files changed, 38 insertions(+)\n>\n> diff --git a/src/libcamera/shaders/bayer_1x_packed.frag b/src/libcamera/shaders/bayer_1x_packed.frag\n> index 77d9fbfa7..eea237dfc 100644\n> --- a/src/libcamera/shaders/bayer_1x_packed.frag\n> +++ b/src/libcamera/shaders/bayer_1x_packed.frag\n> @@ -68,6 +68,19 @@ uniform sampler2D tex_y;\n> uniform mat3 ccm;\n> uniform vec3 blacklevel;\n> uniform float gamma;\n> +uniform float contrast;\n> +\n> +float apply_contrast(float value)\n> +{\n> +\t// Convert 0..2 contrast to 0..infinity; avoid actual infinity at tan(pi/2)\n> +\tfloat contrastExp = tan(clamp(contrast * 0.78539816339744830962, 0.0, 1.5707963267948966 - 0.00001));\n\nCan this be moved to the top level? (The same for the unpacked shader.)\n\n> +\n> +\t// Apply simple S-curve\n> +\tif (value < 0.5)\n> +\t\treturn 0.5 * pow(value / 0.5, contrastExp);\n> +\telse\n> +\t\treturn 1.0 - 0.5 * pow((1.0 - value) / 0.5, contrastExp);\n> +}\n> \n> void main(void)\n> {\n> @@ -261,6 +274,12 @@ void main(void)\n> \trgb.g = (rin * ccm[1][0]) + (gin * ccm[1][1]) + (bin * ccm[1][2]);\n> \trgb.b = (rin * ccm[2][0]) + (gin * ccm[2][1]) + (bin * ccm[2][2]);\n> \n> +\t// Contrast\n> +\trgb = clamp(rgb, 0.0, 1.0);\n> +\trgb.r = apply_contrast(rgb.r);\n> +\trgb.g = apply_contrast(rgb.g);\n> +\trgb.b = apply_contrast(rgb.b);\n> +\n> \t/* Apply gamma after colour correction */\n> \trgb = pow(rgb, vec3(gamma));\n> \n> diff --git a/src/libcamera/shaders/bayer_unpacked.frag b/src/libcamera/shaders/bayer_unpacked.frag\n> index aba11a87f..1226fe075 100644\n> --- a/src/libcamera/shaders/bayer_unpacked.frag\n> +++ b/src/libcamera/shaders/bayer_unpacked.frag\n> @@ -27,6 +27,19 @@ varying vec4 xCoord;\n> uniform mat3 ccm;\n> uniform vec3 blacklevel;\n> uniform float gamma;\n> +uniform float contrast;\n> +\n> +float apply_contrast(float value)\n> +{\n> + // Convert 0..2 contrast to 0..infinity; avoid actual infinity at tan(pi/2)\n> + float contrastExp = tan(clamp(contrast * 0.78539816339744830962, 0.0, 1.5707963267948966 - 0.00001));\n> +\n> + // Apply simple S-curve\n> + if (value < 0.5)\n> + return 0.5 * pow(value / 0.5, contrastExp);\n> + else\n> + return 1.0 - 0.5 * pow((1.0 - value) / 0.5, contrastExp);\n> +}\n> \n> void main(void) {\n> vec3 rgb;\n> @@ -156,6 +169,12 @@ void main(void) {\n> rgb.g = (rin * ccm[1][0]) + (gin * ccm[1][1]) + (bin * ccm[1][2]);\n> rgb.b = (rin * ccm[2][0]) + (gin * ccm[2][1]) + (bin * ccm[2][2]);\n> \n> + // Contrast\n> + rgb = clamp(rgb, 0.0, 1.0);\n> + rgb.r = apply_contrast(rgb.r, contrast);\n> + rgb.g = apply_contrast(rgb.g, contrast);\n> + rgb.b = apply_contrast(rgb.b, contrast);\n> +\n> /* Apply gamma after colour correction */\n> rgb = pow(rgb, vec3(gamma));","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id CDD9AC3257\n\tfor ;\n\tWed, 10 Dec 2025 14:20:55 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 1582A61479;\n\tWed, 10 Dec 2025 15:20:55 +0100 (CET)","from us-smtp-delivery-124.mimecast.com\n\t(us-smtp-delivery-124.mimecast.com [170.10.133.124])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 22C9E613CB\n\tfor ;\n\tWed, 10 Dec 2025 15:20:54 +0100 (CET)","from mail-wm1-f69.google.com (mail-wm1-f69.google.com\n\t[209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS\n\t(version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id\n\tus-mta-244-suRqxKjRM9S2BOwl9rxkYA-1; 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\n\tWed, 10 Dec 2025 06:20:50 -0800 (PST)","by 2002:a05:600c:1991:b0:46e:1a5e:211 with SMTP id\n\t5b1f17b1804b1-47a83843143mr24069105e9.21.1765376449726; \n\tWed, 10 Dec 2025 06:20:49 -0800 (PST)"],"X-Google-Smtp-Source":"AGHT+IFySmI4BjtQKleK4CTeu81JMQXDLDzUG3SIXxv0zM8RQS2wH0QgI3oRNxrPNSQttP3zpJ15rw==","From":"Milan Zamazal ","To":"Bryan O'Donoghue ","Cc":"libcamera-devel@lists.libcamera.org, pavel@ucw.cz","Subject":"Re: [PATCH v7 10/26] libcamera: shaders: Add support for contrast","In-Reply-To":"<20251210005354.44726-11-bryan.odonoghue@linaro.org> (Bryan\n\tO'Donoghue's message of \"Wed, 10 Dec 2025 00:53:38 +0000\")","References":"<20251210005354.44726-1-bryan.odonoghue@linaro.org>\n\t<20251210005354.44726-11-bryan.odonoghue@linaro.org>","Date":"Wed, 10 Dec 2025 15:20:48 +0100","Message-ID":"<854ipy5sfz.fsf@mzamazal-thinkpadp1gen7.tpbc.csb>","User-Agent":"Gnus/5.13 (Gnus v5.13)","MIME-Version":"1.0","X-Mimecast-Spam-Score":"0","X-Mimecast-MFC-PROC-ID":"m5fmq0slMIH8JTBenDQqghHRfhSXQoIXk0oW9ck6sQo_1765376450","X-Mimecast-Originator":"redhat.com","Content-Type":"text/plain","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}}]