[v9,10/26] libcamera: shaders: Add support for contrast
diff mbox series

Message ID 20251217100138.82525-11-bryan.odonoghue@linaro.org
State New
Headers show
Series
  • Add GLES 2.0 GPUISP to libcamera
Related show

Commit Message

Bryan O'Donoghue Dec. 17, 2025, 10:01 a.m. UTC 
Apply contrast after black-level and CCM operations.

Suggested-by: Milan Zamazal <mzamazal@redhat.com>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
---
 src/libcamera/shaders/bayer_1x_packed.frag | 21 +++++++++++++++++++++
 src/libcamera/shaders/bayer_unpacked.frag  | 21 +++++++++++++++++++++
 2 files changed, 42 insertions(+)

Comments

Milan Zamazal Dec. 17, 2025, 1:06 p.m. UTC | #1 
Bryan O'Donoghue <bryan.odonoghue@linaro.org> writes:

> Apply contrast after black-level and CCM operations.
>
> Suggested-by: Milan Zamazal <mzamazal@redhat.com>
> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
> ---
>  src/libcamera/shaders/bayer_1x_packed.frag | 21 +++++++++++++++++++++
>  src/libcamera/shaders/bayer_unpacked.frag  | 21 +++++++++++++++++++++
>  2 files changed, 42 insertions(+)
>
> diff --git a/src/libcamera/shaders/bayer_1x_packed.frag b/src/libcamera/shaders/bayer_1x_packed.frag
> index 77d9fbfa7..0b730070e 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 contrast;
> +
> +float apply_contrast(float value, float contrastExp)
> +{
> +	// 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 +271,17 @@ 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)
> +	 */
> +	float contrastExp = tan(clamp(contrast * 0.78539816339744830962, 0.0, 1.5707963267948966 - 0.00001));

As discussed at the sync, the constants should be either computed from
named constants or explained in a source code comment (here and in the
unpacked shader).

0.78539816339744830962 = pi / 4
1.5707963267948966 = pi / 2

Passing contrastExp value as a uniform is another option.

With either of these:

Reviewed-by: Milan Zamazal <mzamazal@redhat.com>

> +
> +	rgb = clamp(rgb, 0.0, 1.0);
> +	rgb.r = apply_contrast(rgb.r, contrastExp);
> +	rgb.g = apply_contrast(rgb.g, contrastExp);
> +	rgb.b = apply_contrast(rgb.b, contrastExp);
> +
>  	/* 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..114e32058 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           contrast;
> +
> +float apply_contrast(float value, float contrastExp)
> +{
> +    // 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 +166,17 @@ 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
> +     * Convert 0..2 contrast to 0..infinity; avoid actual infinity at tan(pi/2)
> +     */
> +    float contrastExp = tan(clamp(contrast * 0.78539816339744830962, 0.0, 1.5707963267948966 - 0.00001));
> +
> +    rgb = clamp(rgb, 0.0, 1.0);
> +    rgb.r = apply_contrast(rgb.r, contrastExp);
> +    rgb.g = apply_contrast(rgb.g, contrastExp);
> +    rgb.b = apply_contrast(rgb.b, contrastExp);
> +
>      /* Apply gamma after colour correction */
>      rgb = pow(rgb, vec3(gamma));

Patch
diff mbox series 

diff --git a/src/libcamera/shaders/bayer_1x_packed.frag b/src/libcamera/shaders/bayer_1x_packed.frag
index 77d9fbfa7..0b730070e 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 contrast;
+
+float apply_contrast(float value, float contrastExp)
+{
+	// 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 +271,17 @@  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)
+	 */
+	float contrastExp = tan(clamp(contrast * 0.78539816339744830962, 0.0, 1.5707963267948966 - 0.00001));
+
+	rgb = clamp(rgb, 0.0, 1.0);
+	rgb.r = apply_contrast(rgb.r, contrastExp);
+	rgb.g = apply_contrast(rgb.g, contrastExp);
+	rgb.b = apply_contrast(rgb.b, contrastExp);
+
 	/* 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..114e32058 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           contrast;
+
+float apply_contrast(float value, float contrastExp)
+{
+    // 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 +166,17 @@  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
+     * Convert 0..2 contrast to 0..infinity; avoid actual infinity at tan(pi/2)
+     */
+    float contrastExp = tan(clamp(contrast * 0.78539816339744830962, 0.0, 1.5707963267948966 - 0.00001));
+
+    rgb = clamp(rgb, 0.0, 1.0);
+    rgb.r = apply_contrast(rgb.r, contrastExp);
+    rgb.g = apply_contrast(rgb.g, contrastExp);
+    rgb.b = apply_contrast(rgb.b, contrastExp);
+
     /* Apply gamma after colour correction */
     rgb = pow(rgb, vec3(gamma));