Fixed issue with unpremultiplied alpha.

arklumpus · Jan 11, 2021 · aea60b4 · aea60b4
1 parent ff571df
commit aea60b4
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diff --git a/MuPDFCore/MuPDFCore.csproj b/MuPDFCore/MuPDFCore.csproj
@@ -6,7 +6,7 @@
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <Description>MuPDFCore is a set of multiplatform .NET Core bindings for MuPDF. It can render PDF, XPS, EPUB and other formats to raster images returned either as raw bytes, or as image files in multiple formats (including PNG and PSD). It also supports multithreading.</Description>
-    <Version>1.2.0</Version>
+    <Version>1.2.1</Version>
     <PackageIcon>icon.png</PackageIcon>
     <Authors>Giorgio Bianchini</Authors>
     <Company>University of Bristol</Company>

diff --git a/MuPDFCore/MuPDFDocument.cs b/MuPDFCore/MuPDFDocument.cs
@@ -331,15 +331,22 @@ public void Render(int pageNumber, Rectangle region, double zoom, PixelFormats p
                     throw new MuPDFException("Unknown error", result);
             }
 
+            RoundedRectangle roundedRegion = region.Round(fzoom);
+            RoundedSize roundedSize = new RoundedSize(roundedRegion.Width, roundedRegion.Height);
+
+            if (pixelFormat == PixelFormats.RGBA || pixelFormat == PixelFormats.BGRA)
+            {
+                Utils.UnpremultiplyAlpha(destination, roundedSize);
+            }
+
             if (this.ClipToPageBounds && !Pages[pageNumber].Bounds.Contains(DisplayLists[pageNumber].Bounds.Intersect(region)))
             {
-                RoundedRectangle roundedRegion = region.Round(fzoom);
-                Utils.ClipImage(destination, new RoundedSize(roundedRegion.Width, roundedRegion.Height), region, Pages[pageNumber].Bounds, pixelFormat);
+                Utils.ClipImage(destination, roundedSize, region, Pages[pageNumber].Bounds, pixelFormat);
             }
         }
 
         /// <summary>
-        /// Render a page the specified destination.
+        /// Render a page to the specified destination.
         /// </summary>
         /// <param name="pageNumber">The number of the page to render (starting at 0).</param>
         /// <param name="zoom">The scale at which the page will be rendered. This will determine the size in pixel of the image.</param>

diff --git a/MuPDFCore/MuPDFMultiThreadedPageRenderer.cs b/MuPDFCore/MuPDFMultiThreadedPageRenderer.cs
@@ -94,10 +94,18 @@ private void RenderAction()
                     throw new MuPDFException("Unknown error", result);
             }
 
+            RoundedRectangle roundedRegion = this.CurrentRenderData.Region.Round(this.CurrentRenderData.Zoom);
+            RoundedSize roundedSize = new RoundedSize(roundedRegion.Width, roundedRegion.Height);
+
+            if (this.CurrentRenderData.PixelFormat == PixelFormats.RGBA || this.CurrentRenderData.PixelFormat == PixelFormats.BGRA)
+            {
+                Utils.UnpremultiplyAlpha(this.CurrentRenderData.PixelStorage, roundedSize);
+            }
+
             if (this.CurrentRenderData.ClipToPageBounds && !this.CurrentRenderData.PageBounds.Contains(this.CurrentRenderData.DisplayList.Bounds.Intersect(this.CurrentRenderData.Region)))
             {
-                RoundedRectangle roundedRegion = this.CurrentRenderData.Region.Round(this.CurrentRenderData.Zoom);
-                Utils.ClipImage(this.CurrentRenderData.PixelStorage, new RoundedSize(roundedRegion.Width, roundedRegion.Height), this.CurrentRenderData.Region, this.CurrentRenderData.PageBounds, this.CurrentRenderData.PixelFormat);
+
+                Utils.ClipImage(this.CurrentRenderData.PixelStorage, roundedSize, this.CurrentRenderData.Region, this.CurrentRenderData.PageBounds, this.CurrentRenderData.PixelFormat);
             }
         }
 

diff --git a/MuPDFCore/Utils.cs b/MuPDFCore/Utils.cs
@@ -57,7 +57,7 @@ public static bool IsAcceptableNumber(int n)
             if (n == 0)
             {
                 return false;
-            } 
+            }
             else if (n == 1)
             {
                 return true;
@@ -159,5 +159,33 @@ public static void ClipImage(IntPtr image, RoundedSize imageSize, Rectangle imag
                 }
             }
         }
+
+        /// <summary>
+        /// Converts an image with premultiplied alpha values into an image with unpremultiplied alpha values.
+        /// </summary>
+        /// <param name="image">A pointer to the address where the pixel data is stored.</param>
+        /// <param name="imageSize">The size in pixels of the image.</param>
+        public static void UnpremultiplyAlpha(IntPtr image, RoundedSize imageSize)
+        {
+            int stride = imageSize.Width * 4;
+
+            unsafe
+            {
+                byte* imageData = (byte*)image;
+
+                for (int y = 0; y < imageSize.Height; y++)
+                {
+                    for (int x = 0; x < imageSize.Width; x++)
+                    {
+                        if (imageData[y * stride + x * 4 + 3] > 0)
+                        {
+                            imageData[y * stride + x * 4] = (byte)(imageData[y * stride + x * 4] * 255 / imageData[y * stride + x * 4 + 3]);
+                            imageData[y * stride + x * 4 + 1] = (byte)(imageData[y * stride + x * 4 + 1] * 255 / imageData[y * stride + x * 4 + 3]);
+                            imageData[y * stride + x * 4 + 2] = (byte)(imageData[y * stride + x * 4 + 2] * 255 / imageData[y * stride + x * 4 + 3]);
+                        }
+                    }
+                }
+            }
+        }
     }
 }
diff --git a/Readme.md b/Readme.md
@@ -298,7 +298,7 @@ For convenience, these compiled files for MuPDF 1.17.0 are included in the [`nat
 
 ### 2. Building MuPDFWrapper
 
-Once you have the required static library files, you should download the MuPDFCore source code: [MuPDFCore-1.2.0.tar.gz](https://github.com/arklumpus/MuPDFCore/archive/v1.2.0.tar.gz) (or clone the repository) and place the library files in the appropriate subdirectories in the `native/MuPDFWrapper/lib/` folder.
+Once you have the required static library files, you should download the MuPDFCore source code: [MuPDFCore-1.2.1.tar.gz](https://github.com/arklumpus/MuPDFCore/archive/v1.2.1.tar.gz) (or clone the repository) and place the library files in the appropriate subdirectories in the `native/MuPDFWrapper/lib/` folder.
 
 To compile `MuPDFWrapper` you will need [CMake](https://cmake.org/) and (on Windows) [Ninja](https://ninja-build.org/).
 

diff --git a/docs/MuPDFCore.pdf b/docs/MuPDFCore.pdf
diff --git a/docs/_mu_p_d_f_8cs_source.html b/docs/_mu_p_d_f_8cs_source.html
@@ -28,7 +28,7 @@
   <td id="projectlogo"><img alt="Logo" src="icon.svg"/></td>
   <td id="projectalign" style="padding-left: 0.5em;">
    <div id="projectname">MuPDFCore
-   &#160;<span id="projectnumber">1.2.0</span>
+   &#160;<span id="projectnumber">1.2.1</span>
    </div>
    <div id="projectbrief">Multiplatform .NET Core bindings for MuPDF</div>
   </td>

diff --git a/docs/_mu_p_d_f_context_8cs_source.html b/docs/_mu_p_d_f_context_8cs_source.html
@@ -28,7 +28,7 @@
   <td id="projectlogo"><img alt="Logo" src="icon.svg"/></td>
   <td id="projectalign" style="padding-left: 0.5em;">
    <div id="projectname">MuPDFCore
-   &#160;<span id="projectnumber">1.2.0</span>
+   &#160;<span id="projectnumber">1.2.1</span>
    </div>
    <div id="projectbrief">Multiplatform .NET Core bindings for MuPDF</div>
   </td>

diff --git a/docs/_mu_p_d_f_display_list_8cs_source.html b/docs/_mu_p_d_f_display_list_8cs_source.html
@@ -28,7 +28,7 @@
   <td id="projectlogo"><img alt="Logo" src="icon.svg"/></td>
   <td id="projectalign" style="padding-left: 0.5em;">
    <div id="projectname">MuPDFCore
-   &#160;<span id="projectnumber">1.2.0</span>
+   &#160;<span id="projectnumber">1.2.1</span>
    </div>
    <div id="projectbrief">Multiplatform .NET Core bindings for MuPDF</div>
   </td>