Throw ImageFormatException when width or height is 0

src/ImageSharp/Formats/Tga/TgaDecoderCore.cs

@@ -85,6 +85,11 @@ namespace SixLabors.ImageSharp.Formats.Tga
                     TgaThrowHelper.ThrowNotSupportedException($"Unknown tga colormap type {this.fileHeader.ColorMapType} found");
                 }
 
+                if (this.fileHeader.Width == 0 || this.fileHeader.Height == 0)
+                {
+                    throw new UnknownImageFormatException("Width or height cannot be 0");
+                }
+
                 var image = new Image<TPixel>(this.configuration, this.fileHeader.Width, this.fileHeader.Height, this.metadata);
                 Buffer2D<TPixel> pixels = image.GetRootFramePixelBuffer();
 

src/ImageSharp/Formats/Tga/TgaImageFormatDetector.cs

@@ -23,7 +23,13 @@ namespace SixLabors.ImageSharp.Formats.Tga
         {
             if (header.Length >= this.HeaderSize)
             {
-                // There is no magick bytes in a tga file, so at least the image type in the header will be checked for a valid value.
+                // There is no magick bytes in a tga file, so at least the image type
+                // and the colormap type in the header will be checked for a valid value.
+                if (header[1] != 0 && header[1] != 1)
+                {
+                    return false;
+                }
+
                 var imageType = (TgaImageType)header[2];
                 return imageType.IsValid();
             }

tests/ImageSharp.Tests/Formats/Bmp/BmpFileHeaderTests.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.IO;
+using System.Linq;
 
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Formats.Bmp;
@@ -12,10 +13,6 @@ namespace SixLabors.ImageSharp.Tests.Formats.Bmp
 {
     public class BmpFileHeaderTests
     {
-        private static readonly byte[] Data = BitConverter.GetBytes(BmpConstants.TypeMarkers.Bitmap);
-
-        private MemoryStream Stream { get; } = new MemoryStream(Data);
-
         [Fact]
         public void TestWrite()
         {
@@ -27,16 +24,5 @@ namespace SixLabors.ImageSharp.Tests.Formats.Bmp
 
             Assert.Equal("AQACAAAAAwAAAAQAAAA=", Convert.ToBase64String(buffer));
         }
-
-        [Fact]
-        public void ImageLoad_WithoutEnoughData_Throws_UnknownImageFormatException()
-        {
-            Assert.Throws<UnknownImageFormatException>(() =>
-            {
-                using (Image.Load(Configuration.Default, this.Stream, out IImageFormat _))
-                {
-                }
-            });
-        }
     }
 }

tests/ImageSharp.Tests/Formats/Tga/TgaFileHeaderTests.cs

@@ -11,12 +11,16 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tga
 {
     public class TgaFileHeaderTests
     {
-        private static readonly byte[] Data = { 0, 0, 0 };
+        private static readonly byte[] Data = {
+                                                  0,
+                                                  0,
+                                                  15 // invalid tga image type
+                                              };
 
         private MemoryStream Stream { get; } = new MemoryStream(Data);
 
         [Fact]
-        public void ImageLoad_WithoutEnoughData_Throws_UnknownImageFormatException()
+        public void ImageLoad_WithInvalidImageType_Throws_UnknownImageFormatException()
         {
             Assert.Throws<UnknownImageFormatException>(() =>
             {