source: OniSplit/Imaging/TgaReader.cs@ 1142

using System;

namespace Oni.Imaging
{
    internal static class TgaReader
        {
                public static Surface Read(string filePath)
                {
            using (var reader = new BinaryReader(filePath))
                        {
                                var header = TgaHeader.Read(reader);

                                Surface surface;

                                switch (header.ImageType)
                                {
                                        case TgaImageType.TrueColor:
                                                surface = LoadTrueColor(header, reader);
                                                break;

                                        case TgaImageType.RleTrueColor:
                                                surface = LoadRleTrueColor(header, reader);
                                                break;

                                        default:
                                                throw new NotSupportedException(string.Format("Invalid or unsupported TGA image type {0}", header.ImageType));
                                }

                                if (header.XFlip)
                                        surface.FlipHorizontal();

                                if (!header.YFlip)
                                        surface.FlipVertical();

                return surface;
                        }
                }

                private static Surface LoadTrueColor(TgaHeader header, BinaryReader reader)
                {
                        int pixelSize = header.PixelSize;
                        var format = header.GetSurfaceFormat();

                        var dst = new Surface(header.Width, header.Height, format);
                        var src = reader.ReadBytes(header.Width * header.Height * pixelSize);
                        int srcOffset = 0;

                        for (int y = 0; y < header.Height; y++)
                        {
                                for (int x = 0; x < header.Width; x++)
                                {
                                        dst[x, y] = header.GetPixel(src, srcOffset);
                                        srcOffset += pixelSize;
                                }
                        }

                        return dst;
                }

                private static Surface LoadRleTrueColor(TgaHeader header, BinaryReader reader)
                {
                        int pixelSize = header.PixelSize;
                        var format = header.GetSurfaceFormat();

            var dst = new Surface(header.Width, header.Height, format);

                        var src = reader.ReadBytes(reader.Length - reader.Position);
                        int srcOffset = 0;

                        int y = 0;
                        int x = 0;

                        var color = Color.Black;

                        while (y < header.Height)
                        {
                                int packetType = src[srcOffset++];

                                int packetPixelCount = (packetType & 127) + 1;
                                bool isRle = ((packetType & 128) != 0);

                                for (int i = 0; i < packetPixelCount && y < header.Height; i++)
                                {
                                        if (i == 0 || !isRle)
                                        {
                                                color = header.GetPixel(src, srcOffset);
                                                srcOffset += pixelSize;
                                        }

                                        dst[x, y] = color;
                                        x++;

                                        if (x == header.Width)
                                        {
                                                x = 0;
                                                y++;
                                        }
                                }
                        }

                        return dst;
                }
        }
}