Allow TGA and PNG to discard/flatten alpha as desired. Refs #407

* DDS will always save the format entirely literally, and the float
  formats do not support alpha processing currently.
* TGA and PNG will either discard the alpha and write entirely opaque,
  or they'll include it in the file. Blending to colour or checkerboard
  is not supported.

renderdoc/api/replay/replay_enums.h

@@ -188,6 +188,7 @@ enum AlphaMapping
   eAlphaMap_Discard,
   eAlphaMap_BlendToColour,
   eAlphaMap_BlendToCheckerboard,
+  eAlphaMap_Preserve,
 };
 
 enum SpecialFormat

renderdoc/replay/replay_renderer.cpp

@@ -1013,12 +1013,20 @@ bool ReplayRenderer::SaveTexture(const TextureSave &saveData, const char *path)
     }
     else if(sd.destType == eFileType_PNG)
     {
+      // discard alpha if requested
+      for(uint32_t p = 0; sd.alpha == eAlphaMap_Discard && p < td.width * td.height; p++)
+        subdata[0][p * 4 + 3] = 255;
+
       int ret = stbi_write_png_to_func(fileWriteFunc, (void *)f, td.width, td.height, numComps,
                                        subdata[0], rowPitch);
       success = (ret != 0);
     }
     else if(sd.destType == eFileType_TGA)
     {
+      // discard alpha if requested
+      for(uint32_t p = 0; sd.alpha == eAlphaMap_Discard && p < td.width * td.height; p++)
+        subdata[0][p * 4 + 3] = 255;
+
       int ret = stbi_write_tga_to_func(fileWriteFunc, (void *)f, td.width, td.height, numComps,
                                        subdata[0]);
       success = (ret != 0);

renderdocui/Interop/Enums.cs

@@ -191,6 +191,7 @@ namespace renderdoc
         Discard,
         BlendToColour,
         BlendToCheckerboard,
+        Preserve,
     };
 
     public enum SpecialFormat

renderdocui/Windows/Dialogs/TextureSaveDialog.Designer.cs

@@ -275,10 +275,6 @@
             // 
             this.alphaMap.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDownList;
             this.alphaMap.FormattingEnabled = true;
-            this.alphaMap.Items.AddRange(new object[] {
-            "Discard",
-            "Blend to Colour",
-            "Blend to Checkerboard"});
             this.alphaMap.Location = new System.Drawing.Point(89, 3);
             this.alphaMap.Name = "alphaMap";
             this.alphaMap.Size = new System.Drawing.Size(148, 21);

renderdocui/Windows/Dialogs/TextureSaveDialog.cs

@@ -14,6 +14,33 @@ namespace renderdocui.Windows.Dialogs
 {
     public partial class TextureSaveDialog : Form
     {
+        struct AlphaMappingString
+        {
+            public AlphaMappingString(AlphaMapping v)
+            {
+                val = v;
+            }
+
+            public AlphaMapping val;
+
+            public override string ToString()
+            {
+                switch (val)
+                {
+                    case AlphaMapping.Discard:
+                        return "Discard";
+                    case AlphaMapping.BlendToColour:
+                        return "Blend to Colour";
+                    case AlphaMapping.BlendToCheckerboard:
+                        return "Blend To Checkerboard";
+                    case AlphaMapping.Preserve:
+                        return "Preserve";
+                }
+
+                return "";
+            }
+        }
+
         public TextureSaveDialog(Core core)
         {
             InitializeComponent();
@@ -86,8 +113,6 @@ namespace renderdocui.Windows.Dialogs
         {
             jpegCompression.Value = saveData.jpegQuality;
 
-            alphaMap.SelectedIndex = (int)saveData.alpha;
-
             blackPoint.Text = Formatter.Format(saveData.comp.blackPoint);
             whitePoint.Text = Formatter.Format(saveData.comp.whitePoint);
 
@@ -151,7 +176,14 @@ namespace renderdocui.Windows.Dialogs
                     mapSlicesToGrid.Checked = true;
             }
 
+            fileFormat.SelectedIndex = 0;
+            fileFormat.SelectedIndex = 1;
             fileFormat.SelectedIndex = (int)saveData.destType;
+
+            if(saveData.alpha == AlphaMapping.Discard)
+                alphaMap.SelectedIndex = 0;
+            else
+                alphaMap.SelectedIndex = alphaMap.Items.Count - 1;
         }
 
         private void fileFormat_SelectedIndexChanged(object sender, EventArgs e)
@@ -166,7 +198,51 @@ namespace renderdocui.Windows.Dialogs
 
             bool noAlphaFormat = (saveData.destType == FileType.BMP || saveData.destType == FileType.JPG);
 
-            alphaMap.Enabled = (tex.format.compCount == 4 && noAlphaFormat);
+            // any filetype, PNG supporting or not, can choose to preserve or discard the alpha
+            alphaMap.Enabled = tex.format.compCount == 4;
+
+            if (alphaMap.Enabled)
+            {
+                if (noAlphaFormat && alphaMap.Items.Count != 3)
+                {
+                    int idx = (int)alphaMap.SelectedIndex;
+
+                    alphaMap.Items.Clear();
+                    alphaMap.Items.AddRange(new object[] {
+                        new AlphaMappingString(AlphaMapping.Discard),
+                        new AlphaMappingString(AlphaMapping.BlendToColour),
+                        new AlphaMappingString(AlphaMapping.BlendToCheckerboard)
+                    });
+
+                    // if we were discard before, still discard, otherwise blend to checkerboard
+                    if (idx <= 0)
+                        alphaMap.SelectedIndex = 0;
+                    else
+                        alphaMap.SelectedIndex = alphaMap.Items.Count - 1;
+                }
+                else if (alphaMap.Items.Count != 2)
+                {
+                    int idx = (int)alphaMap.SelectedIndex;
+
+                    alphaMap.Items.Clear();
+                    alphaMap.Items.AddRange(new object[] {
+                        new AlphaMappingString(AlphaMapping.Discard),
+                        new AlphaMappingString(AlphaMapping.Preserve)
+                    });
+
+                    // allow the previous selection to clamp, to either discard or preserve
+                    alphaMap.SelectedIndex = Helpers.Clamp(idx, 0, alphaMap.Items.Count-1);
+                }
+            }
+
+            if (alphaMap.Items.Count == 0)
+            {
+                alphaMap.Items.Clear();
+                alphaMap.Items.AddRange(new object[] {
+                    new AlphaMappingString(AlphaMapping.Discard),
+                    new AlphaMappingString(AlphaMapping.Preserve)
+                });
+            }
 
             alphaCol.Enabled = (saveData.alpha == AlphaMapping.BlendToColour && tex.format.compCount == 4 && noAlphaFormat);
 
@@ -198,7 +274,7 @@ namespace renderdocui.Windows.Dialogs
 
         private void alphaMap_SelectedIndexChanged(object sender, EventArgs e)
         {
-            saveData.alpha = (AlphaMapping)alphaMap.SelectedIndex;
+            saveData.alpha = ((AlphaMappingString)alphaMap.SelectedItem).val;
 
             alphaCol.Enabled = (saveData.alpha == AlphaMapping.BlendToColour);
         }
@@ -287,7 +363,7 @@ namespace renderdocui.Windows.Dialogs
 
         private void ok_Click(object sender, EventArgs e)
         {
-            saveData.alpha = (AlphaMapping)alphaMap.SelectedIndex;
+            saveData.alpha = ((AlphaMappingString)alphaMap.SelectedItem).val;
 
             if (saveData.alpha == AlphaMapping.BlendToCheckerboard)
             {

renderdocui/Windows/TextureViewer.cs

@@ -3670,7 +3670,7 @@ namespace renderdocui.Windows
             m_SaveDialog.saveData.comp.blackPoint = m_TexDisplay.rangemin;
             m_SaveDialog.saveData.comp.whitePoint = m_TexDisplay.rangemax;
             m_SaveDialog.saveData.alphaCol = m_TexDisplay.lightBackgroundColour;
-            m_SaveDialog.saveData.alpha = m_TexDisplay.Alpha ? AlphaMapping.BlendToCheckerboard : AlphaMapping.Discard;
+            m_SaveDialog.saveData.alpha = m_TexDisplay.Alpha ? AlphaMapping.Preserve : AlphaMapping.Discard;
             if (m_TexDisplay.Alpha && !checkerBack.Checked) m_SaveDialog.saveData.alpha = AlphaMapping.BlendToColour;
             m_SaveDialog.tex = CurrentTexture;