[libgxps] images: add support for jpeg images with CMYK color space

[Carlos Garcia Campos <carlosgc src gnome org>]

commit 13063c430bbe3621b351924603d7e9b65dc57ea8
Author: Carlos Garcia Campos <cgarcia igalia com>
Date:   Thu Aug 18 17:57:07 2022 +0200

    images: add support for jpeg images with CMYK color space

 libgxps/gxps-images.c | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/libgxps/gxps-images.c b/libgxps/gxps-images.c
index 464d848..ffe1d3c 100644
--- a/libgxps/gxps-images.c
+++ b/libgxps/gxps-images.c
@@ -536,6 +536,12 @@ gxps_images_create_from_jpeg (GXPSArchive *zip,
                                         p[2] = line[0];
                                         p[3] = 0xff;
                                         break;
+                                case JCS_CMYK:
+                                        p[0] = line[2] * line[3] / 255;
+                                        p[1] = line[1] * line[3] / 255;
+                                        p[2] = line[0] * line[3] / 255;
+                                        p[3] = 0xff;
+                                        break;
                                default:
                                        GXPS_DEBUG (g_message ("Unsupported jpeg color space %s",
                                                                _jpeg_color_space_name 
(cinfo.out_color_space)));