BACKENDS: Compress screenshots using PNG if available

Closes gh-948.

3 files changed, 93 insertions, 19 deletions

diff --git a/backends/graphics/opengl/opengl-graphics.cpp b/backends/graphics/opengl/opengl-graphics.cpp
index a595d076db..fc27270648 100644
--- a/backends/graphics/opengl/opengl-graphics.cpp
+++ b/backends/graphics/opengl/opengl-graphics.cpp
@@ -28,6 +28,7 @@
 #include "backends/graphics/opengl/pipelines/shader.h"
 #include "backends/graphics/opengl/shader.h"
 
+#include "common/array.h"
 #include "common/textconsole.h"
 #include "common/translation.h"
 #include "common/algorithm.h"
@@ -43,6 +44,10 @@
 #include "graphics/font.h"
 #endif
 
+#ifdef USE_PNG
+#include "image/png.h"
+#endif
+
 namespace OpenGL {
 
 OpenGLGraphicsManager::OpenGLGraphicsManager()
@@ -1311,33 +1316,35 @@ bool OpenGLGraphicsManager::saveScreenshot(const Common::String &filename) const
 	// Since we use a 3 byte per pixel mode, we can use width % 4 here, since
 	// it is equal to 4 - (width * 3) % 4. (4 - (width * Bpp) % 4, is the
 	// usual way of computing the padding bytes required).
+	// GL_PACK_ALIGNMENT is 4, so this line padding is required for PNG too
 	const uint linePaddingSize = width % 4;
 	const uint lineSize        = width * 3 + linePaddingSize;
 
-	// Allocate memory for screenshot
-	uint8 *pixels = new uint8[lineSize * height];
+	Common::DumpFile out;
+	if (!out.open(filename)) {
+		return false;
+	}
 
-	// Get pixel data from OpenGL buffer
-	GL_CALL(glReadPixels(0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE, pixels));
+	Common::Array<uint8> pixels;
+	pixels.resize(lineSize * height);
+	GL_CALL(glReadPixels(0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE, &pixels.front()));
 
+#ifdef USE_PNG
+	const Graphics::PixelFormat format(3, 8, 8, 8, 0, 16, 8, 0, 0);
+	Graphics::Surface data;
+	data.init(width, height, lineSize, &pixels.front(), format);
+	return Image::writePNG(out, data, true);
+#else
 	// BMP stores as BGR. Since we can't assume that GL_BGR is supported we
 	// will swap the components from the RGB we read to BGR on our own.
 	for (uint y = height; y-- > 0;) {
-		uint8 *line = pixels + y * lineSize;
+		uint8 *line = &pixels.front() + y * lineSize;
 
 		for (uint x = width; x > 0; --x, line += 3) {
 			SWAP(line[0], line[2]);
 		}
 	}
 
-	// Open file
-	Common::DumpFile out;
-	if (!out.open(filename)) {
-		delete[] pixels;
-		return false;
-	}
-
-	// Write BMP header
 	out.writeByte('B');
 	out.writeByte('M');
 	out.writeUint32LE(height * lineSize + 54);
@@ -1354,13 +1361,10 @@ bool OpenGLGraphicsManager::saveScreenshot(const Common::String &filename) const
 	out.writeUint32LE(0);
 	out.writeUint32LE(0);
 	out.writeUint32LE(0);
+	out.write(&pixels.front(), pixels.size());
 
-	// Write pixel data to BMP
-	out.write(pixels, lineSize * height);
-
-	// Free allocated memory
-	delete[] pixels;
 	return true;
+#endif
 }
 
 } // End of namespace OpenGL
diff --git a/backends/graphics/openglsdl/openglsdl-graphics.cpp b/backends/graphics/openglsdl/openglsdl-graphics.cpp
index 75e2cf8ef7..e41148062f 100644
--- a/backends/graphics/openglsdl/openglsdl-graphics.cpp
+++ b/backends/graphics/openglsdl/openglsdl-graphics.cpp
@@ -633,7 +633,11 @@ bool OpenGLSdlGraphicsManager::notifyEvent(const Common::Event &event) {
 				for (int n = 0;; n++) {
 					SDL_RWops *file;
 
+#ifdef USE_PNG
+					filename = Common::String::format("scummvm%05d.png", n);
+#else
 					filename = Common::String::format("scummvm%05d.bmp", n);
+#endif
 
 					file = SDL_RWFromFile((screenshotsPath + filename).c_str(), "r");
 
diff --git a/backends/graphics/surfacesdl/surfacesdl-graphics.cpp b/backends/graphics/surfacesdl/surfacesdl-graphics.cpp
index ccfcc94ab3..9594587d88 100644
--- a/backends/graphics/surfacesdl/surfacesdl-graphics.cpp
+++ b/backends/graphics/surfacesdl/surfacesdl-graphics.cpp
@@ -42,6 +42,10 @@
 #include "graphics/scaler/aspect.h"
 #include "graphics/surface.h"
 #include "gui/EventRecorder.h"
+#ifdef USE_PNG
+#include "common/file.h"
+#include "image/png.h"
+#endif
 
 static const OSystem::GraphicsMode s_supportedShaders[] = {
 	{"NONE", "Normal (no shader)", 0},
@@ -1321,8 +1325,66 @@ void SurfaceSdlGraphicsManager::internUpdateScreen() {
 bool SurfaceSdlGraphicsManager::saveScreenshot(const char *filename) {
 	assert(_hwscreen != NULL);
 
-	Common::StackLock lock(_graphicsMutex);	// Lock the mutex until this function ends
+	Common::StackLock lock(_graphicsMutex);
+#ifdef USE_PNG
+	Common::DumpFile out;
+	if (!out.open(filename)) {
+		return false;
+	}
+
+#if SDL_VERSION_ATLEAST(2, 0, 0)
+	SDL_Surface *rgbScreen = SDL_ConvertSurfaceFormat(_hwscreen, SDL_PIXELFORMAT_RGB24, 0);
+#else
+	// This block of code was taken mostly as-is from SDL 1.2's SDL_SaveBMP_RW
+	SDL_Surface *rgbScreen = SDL_CreateRGBSurface(SDL_SWSURFACE,
+												  _hwscreen->w,
+												  _hwscreen->h,
+												  24,
+#ifdef SCUMM_LITTLE_ENDIAN
+												  0x0000FF, 0x00FF00, 0xFF0000,
+#else
+												  0xFF0000, 0x00FF00, 0x0000FF,
+#endif
+												  0);
+	if (rgbScreen == nullptr) {
+		warning("Could not create RGB24 surface");
+		return false;
+	}
+
+	SDL_Rect bounds;
+	bounds.x = bounds.y = 0;
+	bounds.w = _hwscreen->w;
+	bounds.h = _hwscreen->h;
+	if (SDL_LowerBlit(_hwscreen, &bounds, rgbScreen, &bounds) < 0) {
+		SDL_FreeSurface(rgbScreen);
+		rgbScreen = nullptr;
+	}
+#endif
+
+	if (rgbScreen == nullptr) {
+		warning("Could not convert hardware surface to RGB24");
+		return false;
+	}
+
+	int result = SDL_LockSurface(rgbScreen);
+	if (result < 0) {
+		warning("Could not lock RGB surface");
+		SDL_FreeSurface(rgbScreen);
+		return false;
+	}
+
+	const Graphics::PixelFormat format(3, 8, 8, 8, 0, 16, 8, 0, 0);
+	Graphics::Surface data;
+	data.init(rgbScreen->w, rgbScreen->h, rgbScreen->pitch, rgbScreen->pixels, format);
+	const bool success = Image::writePNG(out, data);
+
+	SDL_UnlockSurface(rgbScreen);
+	SDL_FreeSurface(rgbScreen);
+
+	return success;
+#else
 	return SDL_SaveBMP(_hwscreen, filename) == 0;
+#endif
 }
 
 void SurfaceSdlGraphicsManager::setFullscreenMode(bool enable) {
@@ -2534,7 +2596,11 @@ bool SurfaceSdlGraphicsManager::notifyEvent(const Common::Event &event) {
 			for (int n = 0;; n++) {
 				SDL_RWops *file;
 
+#ifdef USE_PNG
+				filename = Common::String::format("scummvm%05d.png", n);
+#else
 				filename = Common::String::format("scummvm%05d.bmp", n);
+#endif
 
 				file = SDL_RWFromFile((screenshotsPath + filename).c_str(), "r");