(PngIsmFormat): PNG image with inverted alpha-channel.

ArcFormats/Ism/ImagePNG.cs

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+//! \file       ImagePNG.cs
+//! \date       2023 Sep 02
+//! \brief      PNG image with inverted alpha-channel.
+//
+// Copyright (C) 2023 by morkt
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+//
+
+using System.ComponentModel.Composition;
+using System.IO;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+
+namespace GameRes.Formats.Ism
+{
+    [Export(typeof(ImageFormat))]
+    [ExportMetadata("Priority", -1)] // deprioritize
+    public class PngIsmFormat : ImageFormat
+    {
+        public override string         Tag { get => "PNG/ISM"; }
+        public override string Description { get => "ISM engine PNG image"; }
+        public override uint     Signature { get => 0x474e5089; }
+
+        public override ImageMetaData ReadMetaData (IBinaryStream file)
+        {
+            // format only applied when extracting from related archive
+            if (!VFS.IsVirtual || VFS.CurrentArchive.Tag != "ISA")
+                return null;
+            return Png.ReadMetaData (file);
+        }
+
+        public override ImageData Read (IBinaryStream file, ImageMetaData info)
+        {
+            var decoder = new PngBitmapDecoder (file.AsStream,
+                BitmapCreateOptions.None, BitmapCacheOption.OnLoad);
+            BitmapSource bitmap = decoder.Frames[0];
+            if (bitmap.Format != PixelFormats.Bgra32)
+                return new ImageData (bitmap, info);
+            int stride = bitmap.PixelWidth * 4;
+            var pixels = new byte[stride * bitmap.PixelHeight];
+            bitmap.CopyPixels (pixels, stride, 0);
+            for (int i = 3; i < pixels.Length; i += 4)
+            {
+                pixels[i] ^= 0xFF;
+            }
+            return ImageData.Create (info, bitmap.Format, bitmap.Palette, pixels);
+        }
+
+        public override void Write (Stream file, ImageData image)
+        {
+            throw new System.NotImplementedException ("PngIsmFormat.Write not implemented");
+        }
+    }
+}