Relaxed bmp dimensions validation

src/ImageSharp/Formats/Bmp/BmpInfoHeader.cs

@@ -66,6 +66,16 @@ internal struct BmpInfoHeader
         /// </summary>
         public const int HeaderSizeSize = 4;
 
+        /// <summary>
+        /// Maximum dimensions of a bitmap with or height: 2**31 - 1, since width and height are int32
+        /// </summary>
+        private const int MaximumBmpDimension = 2147483647;
+
+        /// <summary>
+        /// Maximum size of a bitmap width * height: 2**32, since size is uint32.
+        /// </summary>
+        private const long MaximumBmpSize = 4294967296;
+
         public BmpInfoHeader(
             int headerSize,
             int width,
@@ -545,13 +555,19 @@ public void WriteV5Header(Span<byte> buffer)
 
         internal void VerifyDimensions()
         {
-            const int MaximumBmpDimension = 65535;
-
             if (this.Width > MaximumBmpDimension || this.Height > MaximumBmpDimension)
             {
                 throw new InvalidOperationException(
-                    $"The input bmp '{this.Width}x{this.Height}' is "
-                    + $"bigger then the max allowed size '{MaximumBmpDimension}x{MaximumBmpDimension}'");
+                    $"The input bmp '{this.Width}x{this.Height}' has a width or height "
+                    + $"bigger then the max allowed '{MaximumBmpDimension}'");
+            }
+
+            long size = this.Width * this.Height;
+            if (size > MaximumBmpSize)
+            {
+                throw new InvalidOperationException(
+                    $"The input bmp '{this.Width}x{this.Height}' has a size {size}"
+                    + $"bigger then the max allowed '{MaximumBmpSize}'");
             }
         }
     }

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

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System;
 using System.IO;
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Formats.Bmp;
@@ -20,6 +21,8 @@ namespace SixLabors.ImageSharp.Tests.Formats.Bmp
     [Trait("Format", "Bmp")]
     public class BmpEncoderTests
     {
+        private static BmpEncoder BmpEncoder => new();
+
         public static readonly TheoryData<BmpBitsPerPixel> BitsPerPixel =
         new()
         {
@@ -50,14 +53,12 @@ public class BmpEncoderTests
         [MemberData(nameof(RatioFiles))]
         public void Encode_PreserveRatio(string imagePath, int xResolution, int yResolution, PixelResolutionUnit resolutionUnit)
         {
-            var options = new BmpEncoder();
-
             var testFile = TestFile.Create(imagePath);
             using (Image<Rgba32> input = testFile.CreateRgba32Image())
             {
                 using (var memStream = new MemoryStream())
                 {
-                    input.Save(memStream, options);
+                    input.Save(memStream, BmpEncoder);
 
                     memStream.Position = 0;
                     using (var output = Image.Load<Rgba32>(memStream))
@@ -75,14 +76,12 @@ public void Encode_PreserveRatio(string imagePath, int xResolution, int yResolut
         [MemberData(nameof(BmpBitsPerPixelFiles))]
         public void Encode_PreserveBitsPerPixel(string imagePath, BmpBitsPerPixel bmpBitsPerPixel)
         {
-            var options = new BmpEncoder();
-
             var testFile = TestFile.Create(imagePath);
             using (Image<Rgba32> input = testFile.CreateRgba32Image())
             {
                 using (var memStream = new MemoryStream())
                 {
-                    input.Save(memStream, options);
+                    input.Save(memStream, BmpEncoder);
 
                     memStream.Position = 0;
                     using (var output = Image.Load<Rgba32>(memStream))
@@ -328,6 +327,21 @@ public void Encode_PreservesColorProfile<TPixel>(TestImageProvider<TPixel> provi
             }
         }
 
+        [Theory]
+        [InlineData(1, 66535)]
+        [InlineData(66535, 1)]
+        public void Encode_WorksWithSizeGreaterThen65k(int width, int height)
+        {
+            Exception exception = Record.Exception(() =>
+            {
+                using Image image = new Image<Rgba32>(width, height);
+                using var memStream = new MemoryStream();
+                image.Save(memStream, BmpEncoder);
+            });
+
+            Assert.Null(exception);
+        }
+
         [Theory]
         [WithFile(Car, PixelTypes.Rgba32, BmpBitsPerPixel.Pixel32)]
         [WithFile(V5Header, PixelTypes.Rgba32, BmpBitsPerPixel.Pixel32)]