From b3c686195fa01434124079a3c8533d6b2f8b9795 Mon Sep 17 00:00:00 2001
From: Paul Gilbert <dreammaster@scummvm.org>
Date: Mon, 21 Nov 2016 20:20:23 -0500
Subject: [PATCH] IMAGE: Add hack to Indeo 4 decoder to guess transparent areas

---
 image/codecs/indeo/indeo.cpp |  4 +++
 image/codecs/indeo/indeo.h   |  5 ++++
 image/codecs/indeo4.cpp      | 48 ++++++++++++++++++++++++++++++++++++
 image/codecs/indeo4.h        |  5 ++++
 4 files changed, 62 insertions(+)

diff --git a/image/codecs/indeo/indeo.cpp b/image/codecs/indeo/indeo.cpp
index f82c4829af91..a20a3ec113aa 100644
--- a/image/codecs/indeo/indeo.cpp
+++ b/image/codecs/indeo/indeo.cpp
@@ -607,6 +607,10 @@ int IndeoDecoderBase::decodeIndeoFrame() {
 	// Free the now un-needed frame data
 	frame->freeFrame();
 
+	// If there's any transparency data, decode it
+	if (_ctx._hasTransp)
+		decodeTransparency();
+
 	return 0;
 }
 
diff --git a/image/codecs/indeo/indeo.h b/image/codecs/indeo/indeo.h
index 068f8c9f25f7..dcb7330318bd 100644
--- a/image/codecs/indeo/indeo.h
+++ b/image/codecs/indeo/indeo.h
@@ -563,6 +563,11 @@ class IndeoDecoderBase : public Codec {
 	*/
 	virtual int decodeMbInfo(IVIBandDesc *band, IVITile *tile) = 0;
 
+	/**
+	 * Decodes optional transparency data within Indeo frames
+	 */
+	virtual void decodeTransparency() {}
+
 	/**
 	 * Decodes the Indeo frame from the bit reader already
 	 * loaded into the context
diff --git a/image/codecs/indeo4.cpp b/image/codecs/indeo4.cpp
index 6141bf0fc86e..b3a5d3a2bf8a 100644
--- a/image/codecs/indeo4.cpp
+++ b/image/codecs/indeo4.cpp
@@ -595,6 +595,54 @@ int Indeo4Decoder::decodeMbInfo(IVIBandDesc *band, IVITile *tile) {
 	return 0;
 }
 
+void Indeo4Decoder::decodeTransparency() {
+	// FIXME: Since I don't currently know how to decode the transparency layer,
+	// I'm currently doing a hack where I take the color of the top left corner,
+	// and mark the range of pixels of that color from the start and end of
+	// each line as transparent
+	assert(_surface->format.bytesPerPixel == 4);
+	byte r, g, b, a;
+
+	if (_surface->format.aBits() == 0) {
+		// Surface is 4 bytes per pixel, but only RGB. So promote the
+		// surface to full RGBA, and convert all the existing pixels
+		Graphics::PixelFormat oldFormat = _pixelFormat;
+		_pixelFormat = Graphics::PixelFormat(4, 8, 8, 8, 8, 24, 16, 8, 0);
+		_surface->format = _pixelFormat;
+
+		for (int y = 0; y < _surface->h; ++y) {
+			uint32 *lineP = (uint32 *)_surface->getBasePtr(0, y);
+			for (int x = 0; x < _surface->w; ++x, ++lineP) {
+				oldFormat.colorToRGB(*lineP, r, g, b);
+				*lineP = _pixelFormat.ARGBToColor(0xff, r, g, b);
+			}
+		}
+	} else {
+		// Working on a frame when the surface is already RGBA. In which case,
+		// start of by defaulting all pixels of the frame to fully opaque
+		for (int y = 0; y < _surface->h; ++y) {
+			uint32 *lineP = (uint32 *)_surface->getBasePtr(0, y);
+			for (int x = 0; x < _surface->w; ++x, ++lineP)
+				*lineP |= 0xff;
+		}
+	}
+
+	// Use the top-left pixel as the key color, and figure out the
+	// equivalent value as fully transparent
+	uint32 keyColor = *(const uint32 *)_surface->getPixels();
+	uint32 transColor = keyColor & ~0xff;
+
+	for (int y = 0; y < _surface->h; ++y) {
+		uint32 *startP = (uint32 *)_surface->getBasePtr(0, y);
+		uint32 *endP = (uint32 *)_surface->getBasePtr(_surface->w - 1, y);
+
+		while (startP <= endP && *startP == keyColor)
+			*startP++ = transColor;
+		while (endP > startP && *endP == keyColor)
+			*endP-- = transColor;
+	}
+}
+
 int Indeo4Decoder::scaleTileSize(int defSize, int sizeFactor) {
 	return sizeFactor == 15 ? defSize : (sizeFactor + 1) << 5;
 }
diff --git a/image/codecs/indeo4.h b/image/codecs/indeo4.h
index 420acc3f33e9..8b7fdab3f9d1 100644
--- a/image/codecs/indeo4.h
+++ b/image/codecs/indeo4.h
@@ -89,6 +89,11 @@ class Indeo4Decoder : public IndeoDecoderBase {
 	 *  @returns       result code: 0 = OK, negative number = error
 	 */
 	virtual int decodeMbInfo(IVIBandDesc *band, IVITile *tile);
+
+	/**
+	 * Decodes optional transparency data within Indeo frames
+	 */
+	virtual void decodeTransparency();
 private:
 	int scaleTileSize(int defSize, int sizeFactor);