utils: Encode high-bit-depth sources to sRGB in screenshots

CMakeLists.txt

@@ -128,6 +128,8 @@ target_sources(
           src/utils/Obs_VolumeMeter_Helpers.h
           src/utils/Platform.cpp
           src/utils/Platform.h
+          src/utils/SourceScreenshot.cpp
+          src/utils/SourceScreenshot.h
           src/utils/Utils.h)
 
 configure_file(src/plugin-macros.h.in plugin-macros.generated.h)

src/requesthandler/RequestHandler_Sources.cpp

@@ -25,84 +25,7 @@ with this program. If not, see <https://www.gnu.org/licenses/>
 
 #include "RequestHandler.h"
 #include "../utils/ImageFormat.h"
-
-QImage TakeSourceScreenshot(obs_source_t *source, bool &success, uint32_t requestedWidth = 0, uint32_t requestedHeight = 0)
-{
-	// Get info about the requested source
-	const uint32_t sourceWidth = obs_source_get_width(source);
-	const uint32_t sourceHeight = obs_source_get_height(source);
-	const double sourceAspectRatio = ((double)sourceWidth / (double)sourceHeight);
-
-	uint32_t imgWidth = sourceWidth;
-	uint32_t imgHeight = sourceHeight;
-
-	// Determine suitable image width
-	if (requestedWidth) {
-		imgWidth = requestedWidth;
-
-		if (!requestedHeight)
-			imgHeight = ((double)imgWidth / sourceAspectRatio);
-	}
-
-	// Determine suitable image height
-	if (requestedHeight) {
-		imgHeight = requestedHeight;
-
-		if (!requestedWidth)
-			imgWidth = ((double)imgHeight * sourceAspectRatio);
-	}
-
-	// Create final image texture
-	QImage ret(imgWidth, imgHeight, QImage::Format::Format_RGBA8888);
-	ret.fill(0);
-
-	// Video image buffer
-	uint8_t *videoData = nullptr;
-	uint32_t videoLinesize = 0;
-
-	// Enter graphics context
-	obs_enter_graphics();
-
-	gs_texrender_t *texRender = gs_texrender_create(GS_RGBA, GS_ZS_NONE);
-	gs_stagesurf_t *stageSurface = gs_stagesurface_create(imgWidth, imgHeight, GS_RGBA);
-
-	success = false;
-	gs_texrender_reset(texRender);
-	if (gs_texrender_begin(texRender, imgWidth, imgHeight)) {
-		vec4 background;
-		vec4_zero(&background);
-
-		gs_clear(GS_CLEAR_COLOR, &background, 0.0f, 0);
-		gs_ortho(0.0f, (float)sourceWidth, 0.0f, (float)sourceHeight, -100.0f, 100.0f);
-
-		gs_blend_state_push();
-		gs_blend_function(GS_BLEND_ONE, GS_BLEND_ZERO);
-
-		obs_source_inc_showing(source);
-		obs_source_video_render(source);
-		obs_source_dec_showing(source);
-
-		gs_blend_state_pop();
-		gs_texrender_end(texRender);
-
-		gs_stage_texture(stageSurface, gs_texrender_get_texture(texRender));
-		if (gs_stagesurface_map(stageSurface, &videoData, &videoLinesize)) {
-			int lineSize = ret.bytesPerLine();
-			for (uint y = 0; y < imgHeight; y++) {
-				memcpy(ret.scanLine(y), videoData + (y * videoLinesize), lineSize);
-			}
-			gs_stagesurface_unmap(stageSurface);
-			success = true;
-		}
-	}
-
-	gs_stagesurface_destroy(stageSurface);
-	gs_texrender_destroy(texRender);
-
-	obs_leave_graphics();
-
-	return ret;
-}
+#include "../utils/SourceScreenshot.h"
 
 bool IsImageFormatValid(std::string format)
 {
@@ -214,7 +137,7 @@ RequestResult RequestHandler::GetSourceScreenshot(const Request &request)
 	}
 
 	bool success;
-	QImage renderedImage = TakeSourceScreenshot(source, success, requestedWidth, requestedHeight);
+	QImage renderedImage = Utils::TakeSourceScreenshot(source, success, requestedWidth, requestedHeight);
 
 	if (!success)
 		return RequestResult::Error(RequestStatus::RequestProcessingFailed, "Failed to render screenshot.");
@@ -309,7 +232,7 @@ RequestResult RequestHandler::SaveSourceScreenshot(const Request &request)
 	}
 
 	bool success;
-	QImage renderedImage = TakeSourceScreenshot(source, success, requestedWidth, requestedHeight);
+	QImage renderedImage = Utils::TakeSourceScreenshot(source, success, requestedWidth, requestedHeight);
 
 	if (!success)
 		return RequestResult::Error(RequestStatus::RequestProcessingFailed, "Failed to render screenshot.");

src/utils/SourceScreenshot.cpp

@@ -0,0 +1,112 @@
+/*
+obs-websocket
+Copyright (C) 2016-2021 Stephane Lepin <stephane.lepin@gmail.com>
+Copyright (C) 2020-2021 Kyle Manning <tt2468@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along
+with this program. If not, see <https://www.gnu.org/licenses/>
+*/
+
+#include <string.h>
+
+#include "SourceScreenshot.h"
+
+QImage Utils::TakeSourceScreenshot(obs_source_t *source, bool &success, uint32_t requestedWidth, uint32_t requestedHeight)
+{
+	// Get info about the requested source
+	const uint32_t sourceWidth = obs_source_get_width(source);
+	const uint32_t sourceHeight = obs_source_get_height(source);
+	const double sourceAspectRatio = ((double)sourceWidth / (double)sourceHeight);
+
+	uint32_t imgWidth = sourceWidth;
+	uint32_t imgHeight = sourceHeight;
+
+	// Determine suitable image width
+	if (requestedWidth) {
+		imgWidth = requestedWidth;
+
+		if (!requestedHeight)
+			imgHeight = ((double)imgWidth / sourceAspectRatio);
+	}
+
+	// Determine suitable image height
+	if (requestedHeight) {
+		imgHeight = requestedHeight;
+
+		if (!requestedWidth)
+			imgWidth = ((double)imgHeight * sourceAspectRatio);
+	}
+
+	// Create final image texture
+	QImage ret(imgWidth, imgHeight, QImage::Format::Format_RGBA8888);
+	ret.fill(0);
+
+	// Video image buffer
+	uint8_t *videoData = nullptr;
+	uint32_t videoLinesize = 0;
+
+	// Enter graphics context
+	obs_enter_graphics();
+
+	gs_texrender_t *texRender = gs_texrender_create(GS_RGBA, GS_ZS_NONE);
+	gs_stagesurf_t *stageSurface = gs_stagesurface_create(imgWidth, imgHeight, GS_RGBA);
+
+	success = false;
+	gs_texrender_reset(texRender);
+	if (gs_texrender_begin(texRender, imgWidth, imgHeight)) {
+		vec4 background;
+		vec4_zero(&background);
+
+		gs_clear(GS_CLEAR_COLOR, &background, 0.0f, 0);
+		gs_ortho(0.0f, (float)sourceWidth, 0.0f, (float)sourceHeight, -100.0f, 100.0f);
+
+		gs_blend_state_push();
+		gs_blend_function(GS_BLEND_ONE, GS_BLEND_ZERO);
+
+		// libobs keeps high-bit-depth sources (P010, I010, I210, I412: HEVC Main10, ProRes, 10-bit
+		// capture cards) as linear float. Scenes and the frontend previews draw with linear sRGB
+		// on, which encodes them to sRGB in an 8-bit target; without it the screenshot is stored
+		// linear and comes out too dark. 8-bit sRGB sources keep the direct path, so their pixels
+		// and straight alpha stay as they were.
+		const enum gs_color_space preferredSpaces[] = {GS_CS_SRGB, GS_CS_SRGB_16F, GS_CS_709_EXTENDED};
+		const enum gs_color_space sourceSpace =
+			obs_source_get_color_space(source, OBS_COUNTOF(preferredSpaces), preferredSpaces);
+		const bool previousLinearSrgb = gs_set_linear_srgb(sourceSpace != GS_CS_SRGB);
+
+		obs_source_inc_showing(source);
+		obs_source_video_render(source);
+		obs_source_dec_showing(source);
+
+		gs_set_linear_srgb(previousLinearSrgb);
+
+		gs_blend_state_pop();
+		gs_texrender_end(texRender);
+
+		gs_stage_texture(stageSurface, gs_texrender_get_texture(texRender));
+		if (gs_stagesurface_map(stageSurface, &videoData, &videoLinesize)) {
+			int lineSize = ret.bytesPerLine();
+			for (uint y = 0; y < imgHeight; y++) {
+				memcpy(ret.scanLine(y), videoData + (y * videoLinesize), lineSize);
+			}
+			gs_stagesurface_unmap(stageSurface);
+			success = true;
+		}
+	}
+
+	gs_stagesurface_destroy(stageSurface);
+	gs_texrender_destroy(texRender);
+
+	obs_leave_graphics();
+
+	return ret;
+}

src/utils/SourceScreenshot.h

@@ -0,0 +1,29 @@
+/*
+obs-websocket
+Copyright (C) 2016-2021 Stephane Lepin <stephane.lepin@gmail.com>
+Copyright (C) 2020-2021 Kyle Manning <tt2468@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along
+with this program. If not, see <https://www.gnu.org/licenses/>
+*/
+
+#pragma once
+
+#include <QImage>
+#include <obs.h>
+
+namespace Utils {
+	// Renders the source on its own into an 8-bit RGBA image of the requested size (0: the
+	// source's own width or height, keeping its aspect ratio). Enters the graphics context.
+	QImage TakeSourceScreenshot(obs_source_t *source, bool &success, uint32_t requestedWidth = 0, uint32_t requestedHeight = 0);
+}