Requests: GetStreamScreenshot

Adds a new request called `GetStreamScreenshot` which returns a
Base64-encoded screenshot of the stream (program).

Author: ghostzero

src/requesthandler/RequestHandler.cpp

@@ -166,6 +166,7 @@ const std::unordered_map<std::string, RequestMethodHandler> RequestHandler::_han
 	{"StartStream", &RequestHandler::StartStream},
 	{"StopStream", &RequestHandler::StopStream},
 	{"SendStreamCaption", &RequestHandler::SendStreamCaption},
+	{"GetStreamScreenshot", &RequestHandler::GetStreamScreenshot},
 
 	// Record
 	{"GetRecordStatus", &RequestHandler::GetRecordStatus},

src/requesthandler/RequestHandler.h

@@ -185,6 +185,7 @@ class RequestHandler {
 	RequestResult StartStream(const Request &);
 	RequestResult StopStream(const Request &);
 	RequestResult SendStreamCaption(const Request &);
+	RequestResult GetStreamScreenshot(const Request &request);
 
 	// Record
 	RequestResult GetRecordStatus(const Request &);

src/requesthandler/RequestHandler_General.cpp

@@ -33,7 +33,7 @@ with this program. If not, see <https://www.gnu.org/licenses/>
  * @responseField obsWebSocketVersion   | String        | Current obs-websocket version
  * @responseField rpcVersion            | Number        | Current latest obs-websocket RPC version
  * @responseField availableRequests     | Array<String> | Array of available RPC requests for the currently negotiated RPC version
- * @responseField supportedImageFormats | Array<String> | Image formats available in `GetSourceScreenshot` and `SaveSourceScreenshot` requests.
+ * @responseField supportedImageFormats | Array<String> | Image formats available in `GetSourceScreenshot`, `SaveSourceScreenshot` and `GetStreamScreenshot` requests.
  * @responseField platform              | String        | Name of the platform. Usually `windows`, `macos`, or `ubuntu` (linux flavor). Not guaranteed to be any of those
  * @responseField platformDescription   | String        | Description of the platform, like `Windows 10 (10.0)`
  *

src/requesthandler/RequestHandler_Stream.cpp

@@ -17,8 +17,98 @@ 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 <QBuffer>
+#include <QImageWriter>
+#include <QFileInfo>
+#include <QImage>
+#include <QDir>
+
 #include "RequestHandler.h"
 
+QImage TakeStreamScreenshot(bool &success, uint32_t requestedWidth = 0, uint32_t requestedHeight = 0)
+{
+	// Get info about the program
+	obs_video_info ovi;
+	obs_get_video_info(&ovi);
+	const uint32_t streamWidth = ovi.base_width;
+	const uint32_t streamHeight = ovi.base_height;
+	const double streamAspectRatio = ((double)streamWidth / (double)streamHeight);
+
+	uint32_t imgWidth = streamWidth;
+	uint32_t imgHeight = streamHeight;
+
+	// Determine suitable image width
+	if (requestedWidth) {
+		imgWidth = requestedWidth;
+
+		if (!requestedHeight)
+			imgHeight = ((double)imgWidth / streamAspectRatio);
+	}
+
+	// Determine suitable image height
+	if (requestedHeight) {
+		imgHeight = requestedHeight;
+
+		if (!requestedWidth)
+			imgWidth = ((double)imgHeight * streamAspectRatio);
+	}
+
+	// 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)streamWidth, 0.0f, (float)streamHeight, -100.0f, 100.0f);
+
+		gs_blend_state_push();
+		gs_blend_function(GS_BLEND_ONE, GS_BLEND_ZERO);
+
+		obs_render_main_texture();
+
+		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;
+}
+
+bool IsStreamImageFormatValid(std::string format)
+{
+	QByteArrayList supportedFormats = QImageWriter::supportedImageFormats();
+	return supportedFormats.contains(format.c_str());
+}
+
 /**
  * Gets the status of the stream output.
  *
@@ -156,3 +246,80 @@ RequestResult RequestHandler::SendStreamCaption(const Request &request)
 
 	return RequestResult::Success();
 }
+
+/**
+ * Gets a Base64-encoded screenshot of the stream.
+ *
+ * The `imageWidth` and `imageHeight` parameters are treated as "scale to inner", meaning the smallest ratio will be used and the aspect ratio of the original resolution is kept.
+ * If `imageWidth` and `imageHeight` are not specified, the compressed image will use the full resolution of the stream.
+ *
+ * @requestField imageFormat              | String | Image compression format to use. Use `GetVersion` to get compatible image formats
+ * @requestField ?imageWidth              | Number | Width to scale the screenshot to                                                                                         | >= 8, <= 4096 | Stream value is used
+ * @requestField ?imageHeight             | Number | Height to scale the screenshot to                                                                                        | >= 8, <= 4096 | Stream value is used
+ * @requestField ?imageCompressionQuality | Number | Compression quality to use. 0 for high compression, 100 for uncompressed. -1 to use "default" (whatever that means, idk) | >= -1, <= 100 | -1
+ *
+ * @responseField imageData | String | Base64-encoded screenshot
+ *
+ * @requestType GetOutputScreenshot
+ * @complexity 4
+ * @rpcVersion -1
+ * @initialVersion 5.4.0
+ * @category stream
+ * @api requests
+ */
+RequestResult RequestHandler::GetStreamScreenshot(const Request &request)
+{
+	RequestStatus::RequestStatus statusCode;
+	std::string comment;
+	std::string imageFormat = request.RequestData["imageFormat"];
+
+	if (!IsStreamImageFormatValid(imageFormat))
+		return RequestResult::Error(RequestStatus::InvalidRequestField,
+					    "Your specified image format is invalid or not supported by this system.");
+
+	uint32_t requestedWidth{0};
+	uint32_t requestedHeight{0};
+	int compressionQuality{-1};
+
+	if (request.Contains("imageWidth")) {
+		if (!request.ValidateOptionalNumber("imageWidth", statusCode, comment, 8, 4096))
+			return RequestResult::Error(statusCode, comment);
+
+		requestedWidth = request.RequestData["imageWidth"];
+	}
+
+	if (request.Contains("imageHeight")) {
+		if (!request.ValidateOptionalNumber("imageHeight", statusCode, comment, 8, 4096))
+			return RequestResult::Error(statusCode, comment);
+
+		requestedHeight = request.RequestData["imageHeight"];
+	}
+
+	if (request.Contains("imageCompressionQuality")) {
+		if (!request.ValidateOptionalNumber("imageCompressionQuality", statusCode, comment, -1, 100))
+			return RequestResult::Error(statusCode, comment);
+
+		compressionQuality = request.RequestData["imageCompressionQuality"];
+	}
+
+	bool success;
+	QImage renderedImage = TakeStreamScreenshot(success, requestedWidth, requestedHeight);
+
+	if (!success)
+		return RequestResult::Error(RequestStatus::RequestProcessingFailed, "Failed to render screenshot.");
+
+	QByteArray encodedImgBytes;
+	QBuffer buffer(&encodedImgBytes);
+	buffer.open(QBuffer::WriteOnly);
+
+	if (!renderedImage.save(&buffer, imageFormat.c_str(), compressionQuality))
+		return RequestResult::Error(RequestStatus::RequestProcessingFailed, "Failed to encode screenshot.");
+
+	buffer.close();
+
+	QString encodedPicture = QString("data:image/%1;base64,").arg(imageFormat.c_str()).append(encodedImgBytes.toBase64());
+
+	json responseData;
+	responseData["imageData"] = encodedPicture.toStdString();
+	return RequestResult::Success(responseData);
+}