public override ImageData Read(IBinaryStream file, ImageMetaData info)
{
using (var reader = new GsaReader(file, (GsaMetaData)info))
{
var pixels = reader.Unpack();
if (PartFileNameRe.IsMatch(file.Name))
{
var base_name = Path.ChangeExtension(file.Name, "GSA");
if (VFS.FileExists(base_name))
{
try
{
var image = TryBlendImage(base_name, reader, info);
if (image != null)
{
return(image);
}
}
catch { /* ignore failed blending attempt */ }
}
}
return(ImageData.CreateFlipped(info, reader.Format, null, pixels, reader.Stride));
}
}
ImageData TryBlendImage(string base_name, GsaReader overlay, ImageMetaData overlay_info)
{
int ovl_x = overlay_info.OffsetX;
int ovl_y = overlay_info.OffsetY;
int ovl_width = (int)overlay_info.Width;
int ovl_height = (int)overlay_info.Height;
if (ovl_x < 0)
{
ovl_width += ovl_x;
ovl_x = 0;
}
if (ovl_y < 0)
{
ovl_height += ovl_y;
ovl_y = 0;
}
using (var input = VFS.OpenBinaryStream(base_name))
{
var base_info = ReadMetaData(input) as GsaMetaData;
if (null == base_info)
{
return(null);
}
int base_width = (int)base_info.Width;
int base_height = (int)base_info.Height;
if (checked (ovl_x + ovl_width) > base_width)
{
ovl_width = base_width - ovl_x;
}
if (checked (ovl_y + ovl_height) > base_height)
{
ovl_height = base_height - ovl_y;
}
if (ovl_height <= 0 || ovl_width <= 0)
{
return(null);
}
input.Position = 0;
var reader = new GsaReader(input, base_info);
var base_pixels = reader.Unpack();
int src_pixel_size = overlay.PixelSize;
int dst_pixel_size = reader.PixelSize;
int dst = ovl_y * reader.Stride + ovl_x * dst_pixel_size;
int src = 0;
for (int y = 0; y < ovl_height; ++y)
{
int src_pixel = src;
int dst_pixel = dst;
for (int x = 0; x < ovl_width; ++x)
{
int src_alpha = overlay.Data[src_pixel + 3];
if (src_alpha > 0)
{
if (0xFF == src_alpha)
{
Buffer.BlockCopy(overlay.Data, src_pixel, base_pixels, dst_pixel, dst_pixel_size);
}
else // assume destination has no alpha channel
{
base_pixels[dst_pixel + 0] = (byte)((overlay.Data[src_pixel + 0] * src_alpha
+ base_pixels[dst_pixel + 0] * (0xFF - src_alpha)) / 0xFF);
base_pixels[dst_pixel + 1] = (byte)((overlay.Data[src_pixel + 1] * src_alpha
+ base_pixels[dst_pixel + 1] * (0xFF - src_alpha)) / 0xFF);
base_pixels[dst_pixel + 2] = (byte)((overlay.Data[src_pixel + 2] * src_alpha
+ base_pixels[dst_pixel + 2] * (0xFF - src_alpha)) / 0xFF);
}
}
src_pixel += src_pixel_size;
dst_pixel += dst_pixel_size;
}
src += overlay.Stride;
dst += reader.Stride;
}
return(ImageData.CreateFlipped(base_info, reader.Format, null, base_pixels, reader.Stride));
}
}