render: introduce bt.1886 transfer function

backend/drm/atomic.c

@@ -188,6 +188,8 @@ static uint8_t convert_cta861_eotf(enum wlr_color_transfer_function tf) {
 		abort(); // unsupported
 	case WLR_COLOR_TRANSFER_FUNCTION_GAMMA22:
 		abort(); // unsupported
+	case WLR_COLOR_TRANSFER_FUNCTION_BT1886:
+		abort(); // unsupported
 	}
 	abort(); // unreachable
 }

include/render/vulkan.h

@@ -154,6 +154,7 @@ enum wlr_vk_texture_transform {
 	WLR_VK_TEXTURE_TRANSFORM_SRGB = 1,
 	WLR_VK_TEXTURE_TRANSFORM_ST2084_PQ = 2,
 	WLR_VK_TEXTURE_TRANSFORM_GAMMA22 = 3,
+	WLR_VK_TEXTURE_TRANSFORM_BT1886 = 4,
 };
 
 enum wlr_vk_shader_source {
@@ -169,6 +170,7 @@ enum wlr_vk_output_transform {
 	WLR_VK_OUTPUT_TRANSFORM_INVERSE_ST2084_PQ = 2,
 	WLR_VK_OUTPUT_TRANSFORM_LUT3D = 3,
 	WLR_VK_OUTPUT_TRANSFORM_INVERSE_GAMMA22 = 4,
+	WLR_VK_OUTPUT_TRANSFORM_INVERSE_BT1886 = 5,
 };
 
 struct wlr_vk_pipeline_key {
@@ -202,6 +204,7 @@ struct wlr_vk_render_format_setup {
 	VkPipeline output_pipe_pq;
 	VkPipeline output_pipe_lut3d;
 	VkPipeline output_pipe_gamma22;
+	VkPipeline output_pipe_bt1886;
 
 	struct wlr_vk_renderer *renderer;
 	struct wl_list pipelines; // struct wlr_vk_pipeline.link

include/wlr/render/color.h

@@ -29,6 +29,7 @@ enum wlr_color_transfer_function {
 	WLR_COLOR_TRANSFER_FUNCTION_ST2084_PQ = 1 << 1,
 	WLR_COLOR_TRANSFER_FUNCTION_EXT_LINEAR = 1 << 2,
 	WLR_COLOR_TRANSFER_FUNCTION_GAMMA22 = 1 << 3,
+	WLR_COLOR_TRANSFER_FUNCTION_BT1886 = 1 << 4,
 };
 
 /**

render/color.c

@@ -202,6 +202,13 @@ void wlr_color_transfer_function_get_default_luminance(enum wlr_color_transfer_f
 			.reference = 203,
 		};
 		break;
+	case WLR_COLOR_TRANSFER_FUNCTION_BT1886:
+		*lum = (struct wlr_color_luminances){
+			.min = 0.01,
+			.max = 100,
+			.reference = 100,
+		};
+		break;
 	default:
 		*lum = (struct wlr_color_luminances){
 			.min = 0.2,

render/vulkan/pass.c

@@ -246,6 +246,9 @@ static bool render_pass_submit(struct wlr_render_pass *wlr_pass) {
 			case WLR_COLOR_TRANSFER_FUNCTION_GAMMA22:
 				pipeline = render_buffer->two_pass.render_setup->output_pipe_gamma22;
 				break;
+			case WLR_COLOR_TRANSFER_FUNCTION_BT1886:
+				pipeline = render_buffer->two_pass.render_setup->output_pipe_bt1886;
+				break;
 			}
 
 			struct wlr_color_luminances srgb_lum, dst_lum;
@@ -799,6 +802,9 @@ static void render_pass_add_texture(struct wlr_render_pass *wlr_pass,
 	case WLR_COLOR_TRANSFER_FUNCTION_GAMMA22:
 		tex_transform = WLR_VK_TEXTURE_TRANSFORM_GAMMA22;
 		break;
+	case WLR_COLOR_TRANSFER_FUNCTION_BT1886:
+		tex_transform = WLR_VK_TEXTURE_TRANSFORM_BT1886;
+		break;
 	}
 
 	struct wlr_vk_pipeline *pipe = setup_get_or_create_pipeline(

render/vulkan/renderer.c

@@ -176,6 +176,7 @@ static void destroy_render_format_setup(struct wlr_vk_renderer *renderer,
 	vkDestroyPipeline(dev, setup->output_pipe_pq, NULL);
 	vkDestroyPipeline(dev, setup->output_pipe_lut3d, NULL);
 	vkDestroyPipeline(dev, setup->output_pipe_gamma22, NULL);
+	vkDestroyPipeline(dev, setup->output_pipe_bt1886, NULL);
 
 	struct wlr_vk_pipeline *pipeline, *tmp_pipeline;
 	wl_list_for_each_safe(pipeline, tmp_pipeline, &setup->pipelines, link) {
@@ -2351,6 +2352,11 @@ static struct wlr_vk_render_format_setup *find_or_create_render_setup(
 				&setup->output_pipe_gamma22, WLR_VK_OUTPUT_TRANSFORM_INVERSE_GAMMA22)) {
 			goto error;
 		}
+		if (!init_blend_to_output_pipeline(
+			renderer, setup->render_pass, renderer->output_pipe_layout,
+			&setup->output_pipe_bt1886, WLR_VK_OUTPUT_TRANSFORM_INVERSE_BT1886)) {
+			goto error;
+		}
 	} else {
 		assert(format->vk_srgb);
 		VkAttachmentDescription attachment = {

render/vulkan/shaders/output.frag

@@ -23,6 +23,7 @@ layout (constant_id = 0) const int OUTPUT_TRANSFORM = 0;
 #define OUTPUT_TRANSFORM_INVERSE_ST2084_PQ 2
 #define OUTPUT_TRANSFORM_LUT_3D 3
 #define OUTPUT_TRANSFORM_INVERSE_GAMMA22 4
+#define OUTPUT_TRANSFORM_INVERSE_BT1886 5
 
 float linear_channel_to_srgb(float x) {
 	return max(min(x * 12.92, 0.04045), 1.055 * pow(x, 1. / 2.4) - 0.055);
@@ -47,6 +48,14 @@ vec3 linear_color_to_pq(vec3 color) {
 	return pow((vec3(c1) + c2 * pow_n) / (vec3(1) + c3 * pow_n), vec3(m));
 }
 
+vec3 linear_color_to_bt1886(vec3 color) {
+	float lb = pow(0.0001, 1.0 / 2.4);
+	float lw = pow(1.0, 1.0 / 2.4);
+	float a  = pow(lw - lb, 2.4);
+	float b  = lb / (lw - lb);
+	return pow(color / a, vec3(1.0 / 2.4)) - vec3(b);
+}
+
 void main() {
 	vec4 in_color = subpassLoad(in_color).rgba;
 
@@ -74,6 +83,8 @@ void main() {
 		rgb = linear_color_to_srgb(rgb);
 	} else if (OUTPUT_TRANSFORM == OUTPUT_TRANSFORM_INVERSE_GAMMA22) {
 		rgb = pow(rgb, vec3(1. / 2.2));
+	} else if (OUTPUT_TRANSFORM == OUTPUT_TRANSFORM_INVERSE_BT1886) {
+		rgb = linear_color_to_bt1886(rgb);
 	}
 
 	// Back to pre-multiplied alpha

render/vulkan/shaders/texture.frag

@@ -19,6 +19,7 @@ layout (constant_id = 0) const int TEXTURE_TRANSFORM = 0;
 #define TEXTURE_TRANSFORM_SRGB 1
 #define TEXTURE_TRANSFORM_ST2084_PQ 2
 #define TEXTURE_TRANSFORM_GAMMA22 3
+#define TEXTURE_TRANSFORM_BT1886 4
 
 float srgb_channel_to_linear(float x) {
 	return mix(x / 12.92,
@@ -45,6 +46,14 @@ vec3 pq_color_to_linear(vec3 color) {
 	return pow(num / denom, vec3(inv_m1));
 }
 
+vec3 bt1886_color_to_linear(vec3 color) {
+	float lb = pow(0.0001, 1.0 / 2.4);
+	float lw = pow(1.0, 1.0 / 2.4);
+	float a  = pow(lw - lb, 2.4);
+	float b  = lb / (lw - lb);
+	return a * pow(color + vec3(b), vec3(2.4));
+}
+
 void main() {
 	vec4 in_color = textureLod(tex, uv, 0);
 
@@ -63,6 +72,8 @@ void main() {
 		rgb = pq_color_to_linear(rgb);
 	} else if (TEXTURE_TRANSFORM == TEXTURE_TRANSFORM_GAMMA22) {
 		rgb = pow(rgb, vec3(2.2));
+	} else if (TEXTURE_TRANSFORM == TEXTURE_TRANSFORM_BT1886) {
+		rgb = bt1886_color_to_linear(rgb);
 	}
 
 	rgb *= data.luminance_multiplier;

types/scene/surface.c

@@ -41,6 +41,7 @@ static bool get_tf_preference(enum wlr_color_transfer_function tf) {
 		return 0;
 	case WLR_COLOR_TRANSFER_FUNCTION_ST2084_PQ:
 		return 1;
+	case WLR_COLOR_TRANSFER_FUNCTION_BT1886:
 	case WLR_COLOR_TRANSFER_FUNCTION_SRGB:
 	case WLR_COLOR_TRANSFER_FUNCTION_EXT_LINEAR:
 		return -1;

types/wlr_color_management_v1.c

@@ -995,6 +995,8 @@ wlr_color_manager_v1_transfer_function_to_wlr(enum wp_color_manager_v1_transfer_
 		return WLR_COLOR_TRANSFER_FUNCTION_EXT_LINEAR;
 	case WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_GAMMA22:
 		return WLR_COLOR_TRANSFER_FUNCTION_GAMMA22;
+	case WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_BT1886:
+		return WLR_COLOR_TRANSFER_FUNCTION_BT1886;
 	default:
 		abort();
 	}
@@ -1011,6 +1013,8 @@ wlr_color_manager_v1_transfer_function_from_wlr(enum wlr_color_transfer_function
 		return WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_EXT_LINEAR;
 	case WLR_COLOR_TRANSFER_FUNCTION_GAMMA22:
 		return WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_GAMMA22;
+	case WLR_COLOR_TRANSFER_FUNCTION_BT1886:
+		return WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_BT1886;
 	}
 	abort();
 }