Fix Black thumbnail when adding cover via scraping.

The `ThumbnailImage.CreateFrom` used when adding thumbnail via `AddCustomThumbnail` that the plugins uses.

It would only work with the `ThumbnailResampling = FastBilinear`. These custom thumbnail are the only that support transparency and are saved in PNG format.

The code that forced creating the alpha channel was moved out of the general resize code and inside only Billinear. So only that resampling would create a proper 32bit image.

Author: maforget

ComicRack.Engine/IO/ThumbnailImage.cs

@@ -151,7 +151,9 @@ public static ThumbnailImage CreateFrom(Bitmap image, Size originalSize, bool su
 			ThumbnailImage thumbnailImage;
 			using (Image image2 = Scale(image, new Size(0, MaxHeight)))
 			{
-				thumbnailImage = ((!supportTransparent) ? new ThumbnailImage(image2.ImageToJpegBytes(ThumbnailQuality), image2.Size, originalSize) : new ThumbnailImage(image2.ImageToBytes(ImageFormat.Png), image2.Size, originalSize));
+                thumbnailImage = supportTransparent
+					? new ThumbnailImage(image2.ImageToBytes(ImageFormat.Png), image2.Size, originalSize)
+					: new ThumbnailImage(image2.ImageToJpegBytes(ThumbnailQuality), image2.Size, originalSize);
 			}
 			if (lastRequestHeight != 0)
 			{

cYo.Common/Drawing/ImageProcessing.cs

@@ -948,7 +948,11 @@ public unsafe static Bitmap ResizeFast(Bitmap source, int newWidth, int newHeigh
                 byte* orgsrc = (byte*)srcData.Scan0.ToPointer();
 				byte* orgdst = (byte*)dstData.Scan0.ToPointer();
 
-                switch (method)
+				//Image has 4 bytesPerPixel (32 bit), so Add Alpha Channel
+				if (dstPixelSize == 4)
+					InitializeAlpha32(orgdst, newWidth, newHeight, dstStride);
+
+				switch (method)
 				{
 						case ResizeFastInterpolation.NearestNeighbor:
                         // for each line
@@ -973,10 +977,6 @@ public unsafe static Bitmap ResizeFast(Bitmap source, int newWidth, int newHeigh
 						break;
 						case ResizeFastInterpolation.Bilinear:
                         {
-                            //Image has 4 bytesPerPixel (32 bit), so Add Alpha Channel
-                            if (dstPixelSize == 4)
-                                InitializeAlpha32(orgdst, newWidth, newHeight, dstStride);
-
                             // Ref: https://github.com/andrewkirillov/AForge.NET/blob/master/Sources/Imaging/Filters/Transform/ResizeBilinear.cs#L78
                             // width and height decreased by 1
                             int ymax = height - 1;
@@ -1027,14 +1027,9 @@ public unsafe static Bitmap ResizeFast(Bitmap source, int newWidth, int newHeigh
                         }
 						case ResizeFastInterpolation.Bicubic:
                         {
-                            // Zero-initialize entire buffer for accumulation
-                            byte* initDst = orgdst;
-                            for (int i = 0; i < newHeight * dstStride; i++)
-                                *initDst++ = 0;
-
-                            // Ref: https://github.com/andrewkirillov/AForge.NET/blob/master/Sources/Imaging/Filters/Transform/ResizeBicubic.cs#L79
-                            // width and height decreased by 1
-                            int ymax = height - 1;
+							// Ref: https://github.com/andrewkirillov/AForge.NET/blob/master/Sources/Imaging/Filters/Transform/ResizeBicubic.cs#L79
+							// width and height decreased by 1
+							int ymax = height - 1;
                             int xmax = width - 1;
 
                             Parallel.For(0, newHeight, (int y) =>