render/color: introduce wlr_color_transform

.builds/alpine.yml

@@ -3,6 +3,7 @@ packages:
   - eudev-dev
   - ffmpeg-dev
   - glslang
+  - lcms2-dev
   - libinput-dev
   - libxkbcommon-dev
   - mesa-dev

.builds/archlinux.yml

@@ -2,6 +2,7 @@ image: archlinux
 packages:
   - clang
   - ffmpeg
+  - lcms2
   - libinput
   - libxkbcommon
   - mesa

.builds/freebsd.yml

@@ -6,6 +6,7 @@ packages:
   - devel/meson # implies ninja
   - devel/pkgconf
   - graphics/glslang
+  - graphics/lcms2
   - graphics/libdrm
   - graphics/mesa-libs
   - graphics/png

include/wlr/render/color.h

@@ -0,0 +1,44 @@
+/*
+ * This an unstable interface of wlroots. No guarantees are made regarding the
+ * future consistency of this API.
+ */
+#ifndef WLR_USE_UNSTABLE
+#error "Add -DWLR_USE_UNSTABLE to enable unstable wlroots features"
+#endif
+
+#ifndef WLR_RENDER_COLOR_H
+#define WLR_RENDER_COLOR_H
+
+#include <stdbool.h>
+#include <sys/types.h>
+
+/**
+ * A color transformation formula.
+ *
+ * The formula is approximated via a 3D look-up table. A 3D LUT is a
+ * three-dimensional array where each element is an RGB triplet. The flat lut_3d
+ * array has a length of dim_len³.
+ *
+ * Color channel values in the range [0.0, 1.0] are mapped linearly to
+ * 3D LUT indices such that 0.0 maps exactly to the first element and 1.0 maps
+ * exactly to the last element in each dimension.
+ *
+ * The offset of the RGB triplet given red, green and blue indices r_index,
+ * g_index and b_index is:
+ *
+ *     offset = 3 * (r_index + dim_len * g_index + dim_len * dim_len * b_index)
+ */
+struct wlr_color_transform {
+	float *lut_3d;
+	size_t dim_len;
+};
+
+/**
+ * Initialize a color transformation to convert sRGB to an ICC profile.
+ */
+bool wlr_color_transform_init_srgb_to_icc(struct wlr_color_transform *tr,
+	const void *data, size_t size);
+
+void wlr_color_transform_finish(struct wlr_color_transform *tr);
+
+#endif

meson_options.txt

@@ -7,3 +7,4 @@ option('backends', type: 'array', choices: ['auto', 'drm', 'libinput', 'x11'], v
 option('allocators', type: 'array', choices: ['auto', 'gbm'], value: ['auto'],
 	description: 'Select built-in allocators')
 option('session', type: 'feature', value: 'auto', description: 'Enable session support')
+option('color-management', type: 'feature', value: 'auto', description: 'Enable support for color management')

render/color.c

@@ -0,0 +1,94 @@
+#include <lcms2.h>
+#include <stdlib.h>
+#include <wlr/render/color.h>
+#include <wlr/util/log.h>
+
+static void handle_lcms_error(cmsContext ctx, cmsUInt32Number code, const char *text) {
+	wlr_log(WLR_ERROR, "[lcms] %s", text);
+}
+
+bool wlr_color_transform_init_srgb_to_icc(struct wlr_color_transform *tr,
+		const void *data, size_t size) {
+	bool ok = false;
+
+	cmsContext ctx = cmsCreateContext(NULL, NULL);
+	if (ctx == NULL) {
+		wlr_log(WLR_ERROR, "cmsCreateContext failed");
+		return false;
+	}
+
+	cmsSetLogErrorHandlerTHR(ctx, handle_lcms_error);
+
+	cmsHPROFILE icc_profile = cmsOpenProfileFromMemTHR(ctx, data, size);
+	if (icc_profile == NULL) {
+		wlr_log(WLR_ERROR, "cmsOpenProfileFromMemTHR failed");
+		goto out_ctx;
+	}
+
+	if (cmsGetDeviceClass(icc_profile) != cmsSigDisplayClass) {
+		wlr_log(WLR_ERROR, "ICC profile must have the Display device class");
+		goto out_icc_profile;
+	}
+
+	cmsHPROFILE srgb_profile = cmsCreate_sRGBProfile();
+	if (srgb_profile == NULL) {
+		wlr_log(WLR_ERROR, "cmsCreate_sRGBProfile failed");
+		goto out_icc_profile;
+	}
+
+	cmsHTRANSFORM lcms_tr = cmsCreateTransformTHR(ctx,
+		srgb_profile, TYPE_RGB_FLT, icc_profile, TYPE_RGB_FLT,
+		INTENT_RELATIVE_COLORIMETRIC, 0);
+	if (lcms_tr == NULL) {
+		wlr_log(WLR_ERROR, "cmsCreateTransformTHR failed");
+		goto out_srgb_profile;
+	}
+
+	size_t dim_len = 33;
+	float *lut_3d = calloc(3 * dim_len * dim_len * dim_len, sizeof(float));
+	if (lut_3d == NULL) {
+		wlr_log_errno(WLR_ERROR, "Allocation failed");
+		goto out_lcms_tr;
+	}
+
+	float factor = 1.0f / (dim_len - 1);
+	for (size_t b_index = 0; b_index < dim_len; b_index++) {
+		for (size_t g_index = 0; g_index < dim_len; g_index++) {
+			for (size_t r_index = 0; r_index < dim_len; r_index++) {
+				float rgb_in[3] = {
+					r_index * factor,
+					g_index * factor,
+					b_index * factor,
+				};
+				float rgb_out[3];
+				cmsDoTransform(lcms_tr, rgb_in, rgb_out, 1);
+
+				size_t offset = 3 * (r_index + dim_len * g_index + dim_len * dim_len * b_index);
+				// TODO: maybe clamp values to [0.0, 1.0] here?
+				lut_3d[offset] = rgb_out[0];
+				lut_3d[offset + 1] = rgb_out[1];
+				lut_3d[offset + 2] = rgb_out[2];
+			}
+		}
+	}
+
+	ok = true;
+	*tr = (struct wlr_color_transform){
+		.lut_3d = lut_3d,
+		.dim_len = dim_len,
+	};
+
+out_lcms_tr:
+	cmsDeleteTransform(lcms_tr);
+out_srgb_profile:
+	cmsCloseProfile(srgb_profile);
+out_icc_profile:
+	cmsCloseProfile(icc_profile);
+out_ctx:
+	cmsDeleteContext(ctx);
+	return ok;
+}
+
+void wlr_color_transform_finish(struct wlr_color_transform *tr) {
+	free(tr->lut_3d);
+}

render/meson.build

@@ -38,3 +38,9 @@ endif
 subdir('pixman')
 
 subdir('allocator')
+
+lcms2 = dependency('lcms2', required: get_option('color-management'))
+if lcms2.found()
+	wlr_deps += lcms2
+	wlr_files += files('color.c')
+endif