3 files changed, 68 insertions, 30 deletions

diff --git a/backends/graphics/opengl/opengl-graphics.cpp b/backends/graphics/opengl/opengl-graphics.cpp
index cfddc93e2f..ad6094b9a1 100644
--- a/backends/graphics/opengl/opengl-graphics.cpp
+++ b/backends/graphics/opengl/opengl-graphics.cpp
@@ -46,6 +46,8 @@
 
 #ifdef USE_PNG
 #include "image/png.h"
+#else
+#include "image/bmp.h"
 #endif
 
 namespace OpenGL {
@@ -1212,41 +1214,13 @@ bool OpenGLGraphicsManager::saveScreenshot(const Common::String &filename) const
 	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);
+#ifdef USE_PNG
 	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.front() + y * lineSize;
-
-		for (uint x = width; x > 0; --x, line += 3) {
-			SWAP(line[0], line[2]);
-		}
-	}
-
-	out.writeByte('B');
-	out.writeByte('M');
-	out.writeUint32LE(height * lineSize + 54);
-	out.writeUint32LE(0);
-	out.writeUint32LE(54);
-	out.writeUint32LE(40);
-	out.writeUint32LE(width);
-	out.writeUint32LE(height);
-	out.writeUint16LE(1);
-	out.writeUint16LE(24);
-	out.writeUint32LE(0);
-	out.writeUint32LE(0);
-	out.writeUint32LE(0);
-	out.writeUint32LE(0);
-	out.writeUint32LE(0);
-	out.writeUint32LE(0);
-	out.write(&pixels.front(), pixels.size());
-
-	return true;
+	return Image::writeBMP(out, data, true);
 #endif
 }
 
diff --git a/image/bmp.cpp b/image/bmp.cpp
index 28eb049035..ce2b099797 100644
--- a/image/bmp.cpp
+++ b/image/bmp.cpp
@@ -132,4 +132,59 @@ bool BitmapDecoder::loadStream(Common::SeekableReadStream &stream) {
 	return true;
 }
 
+bool writeBMP(Common::WriteStream &out, const Graphics::Surface &input, const bool bottomUp) {
+	const Graphics::PixelFormat requiredFormat_3byte(3, 8, 8, 8, 0, 0, 8, 16, 0);
+
+	Graphics::Surface *tmp = NULL;
+	const Graphics::Surface *surface;
+
+	if (input.format == requiredFormat_3byte) {
+		surface = &input;
+	} else {
+		surface = tmp = input.convertTo(requiredFormat_3byte);
+	}
+
+	int dstPitch = surface->w * 3;
+	int extraDataLength = (dstPitch % 4) ? 4 - (dstPitch % 4) : 0;
+	int padding = 0;
+
+	out.writeByte('B');
+	out.writeByte('M');
+	out.writeUint32LE(surface->h * dstPitch + 54);
+	out.writeUint32LE(0);
+	out.writeUint32LE(54);
+	out.writeUint32LE(40);
+	out.writeUint32LE(surface->w);
+	out.writeUint32LE(surface->h);
+	out.writeUint16LE(1);
+	out.writeUint16LE(24);
+	out.writeUint32LE(0);
+	out.writeUint32LE(0);
+	out.writeUint32LE(0);
+	out.writeUint32LE(0);
+	out.writeUint32LE(0);
+	out.writeUint32LE(0);
+
+
+	if (bottomUp) {
+		for (uint y = 0; y < surface->h; ++y) {
+			out.write((const void *)surface->getBasePtr(0, y), dstPitch);
+			out.write(&padding, extraDataLength);
+		}
+	} else {
+		for (uint y = surface->h; y-- > 0;) {
+			out.write((const void *)surface->getBasePtr(0, y), dstPitch);
+			out.write(&padding, extraDataLength);
+		}
+	}
+
+	// free tmp surface
+	if (tmp) {
+		tmp->free();
+		delete tmp;
+	}
+
+	return true;
+}
+
 } // End of namespace Image
diff --git a/image/bmp.h b/image/bmp.h
index b482cc674b..a23f1e0978 100644
--- a/image/bmp.h
+++ b/image/bmp.h
@@ -37,6 +37,7 @@
 
 namespace Common {
 class SeekableReadStream;
+class WriteStream;
 }
 
 namespace Graphics {
@@ -66,6 +67,14 @@ private:
 	uint16 _paletteColorCount;
 };
 
+/**
+ * Outputs an uncompressed BMP stream of the given input surface.
+ *
+ * @param bottomUp Flip the vertical axis so pixel data is drawn from the
+ * bottom up, instead of from the top down.
+ */
+bool writeBMP(Common::WriteStream &out, const Graphics::Surface &input, const bool bottomUp = false);
+
 } // End of namespace Image
 
 #endif