Merge pull request #149 from JimBobSquarePants/tocsoft/point-as-pixel

Default text drawing at an image dpi independent size

src/ImageSharp.Drawing/Text/DrawText.cs

@@ -18,6 +18,8 @@ namespace ImageSharp
     /// </summary>
     public static partial class ImageExtensions
     {
+        private static readonly Vector2 DefaultTextDpi = new Vector2(72);
+
         /// <summary>
         /// Draws the text onto the the image filled via the brush.
         /// </summary>
@@ -169,7 +171,12 @@ namespace ImageSharp
 
             TextRenderer renderer = new TextRenderer(glyphBuilder);
 
-            Vector2 dpi = new Vector2((float)source.MetaData.HorizontalResolution, (float)source.MetaData.VerticalResolution);
+            Vector2 dpi = DefaultTextDpi;
+            if (options.UseImageResolution)
+            {
+                dpi = new Vector2((float)source.MetaData.HorizontalResolution, (float)source.MetaData.VerticalResolution);
+            }
+
             FontSpan style = new FontSpan(font)
             {
                 ApplyKerning = options.ApplyKerning,

src/ImageSharp.Drawing/Text/TextGraphicsOptions.cs

@@ -35,6 +35,12 @@ namespace ImageSharp.Drawing
         /// </summary>
         public float TabWidth;
 
+        /// <summary>
+        /// Flag weather to use the current image resultion to for point size scaling.
+        /// If this is [false] the text renders at 72dpi otherwise it renders at Image resolution
+        /// </summary>
+        public bool UseImageResolution;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="TextGraphicsOptions" /> struct.
         /// </summary>
@@ -45,6 +51,7 @@ namespace ImageSharp.Drawing
             this.ApplyKerning = true;
             this.TabWidth = 4;
             this.AntialiasSubpixelDepth = 16;
+            this.UseImageResolution = false;
         }
 
         /// <summary>

tests/ImageSharp.Tests/Drawing/Text/DrawText.cs

@@ -219,5 +219,32 @@ namespace ImageSharp.Tests.Drawing.Text
             Assert.IsType<FillRegionProcessor<Color>>(this.img.ProcessorApplications[0].processor);
             Assert.IsType<DrawPathProcessor<Color>>(this.img.ProcessorApplications[1].processor);
         }
+
+        [Fact]
+        public void GlyphHeightChangesBasedOnuseImageResolutionFlag()
+        {
+            this.img.MetaData.VerticalResolution = 1;
+            this.img.MetaData.HorizontalResolution = 1;
+            this.img.DrawText("1", this.Font, Brushes.Solid(Color.Red), Vector2.Zero, new TextGraphicsOptions(true) {
+                UseImageResolution = false
+            });
+
+            this.img.DrawText("1", this.Font, Brushes.Solid(Color.Red), Vector2.Zero, new TextGraphicsOptions(true)
+            {
+                UseImageResolution = true
+            });
+
+            Assert.NotEmpty(this.img.ProcessorApplications);
+            Assert.Equal(2, this.img.ProcessorApplications.Count);
+            FillRegionProcessor<Color> ownResolution = Assert.IsType<FillRegionProcessor<Color>>(this.img.ProcessorApplications[0].processor);
+            FillRegionProcessor<Color> imgResolution = Assert.IsType<FillRegionProcessor<Color>>(this.img.ProcessorApplications[1].processor);
+
+            ShapeRegion ownRegion = Assert.IsType<ShapeRegion>(ownResolution.Region);
+            ShapeRegion imgRegion = Assert.IsType<ShapeRegion>(imgResolution.Region);
+
+            // magic numbers based on the font used at well known resolutions
+            Assert.Equal(7.44, ownRegion.Shape.Bounds.Height, 2);
+            Assert.Equal(0.1, imgRegion.Shape.Bounds.Height, 2);
+        }
     }
 }