From de03b0de95c09f64acb66ab2e694d1c4e51a49ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Ko=C5=82odziejski?= <aquadran@gmail.com>
Date: Tue, 5 Jul 2022 21:33:03 +0200
Subject: [PATCH] IMAGES: Added comments describing use case for CMYK color
 space format

---
 image/jpeg.cpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/image/jpeg.cpp b/image/jpeg.cpp
index 0cd4df41db4..ffb197ae005 100644
--- a/image/jpeg.cpp
+++ b/image/jpeg.cpp
@@ -271,8 +271,13 @@ bool JPEGDecoder::loadStream(Common::SeekableReadStream &stream) {
 		break;
 	}
 
-	if (cinfo.num_components == 4)
+	// Semi-hack:
+	// In case 4 components jpeglib expect CMYK or CYYK color space output.
+	// To avoid any color space conversion, CMYK must be used.
+	// HPL1 engine use it to pass RGBA jpeg bitmaps.
+	if (cinfo.num_components == 4) {
 		cinfo.out_color_space = JCS_CMYK;
+	}
 
 	// Actually start decompressing the image
 	jpeg_start_decompress(&cinfo);
@@ -297,6 +302,10 @@ bool JPEGDecoder::loadStream(Common::SeekableReadStream &stream) {
 	default:
 		break;
 	}
+	// Size of output pixel must match 4 bytes.
+	if (cinfo.out_color_space == JCS_CMYK) {
+		assert(_surface.format.bytesPerPixel == 4);
+	}
 
 	// Allocate buffer for one scanline
 	JDIMENSION pitch = cinfo.output_width * _surface.format.bytesPerPixel;