XV-Display: refine the formulation of the image-generator

- since we now use 32bit int arithmetic (which is faster),
   we can also use the exact value of the MPEG / Rec.601 coefficients

 - and also the generation of the NTSC colour bar pattern
   can be written much simpler and cleare with C++

src/steam/engine/worker/dummy-image-generator.cpp

@@ -43,9 +43,9 @@ namespace node {
       auto b = int(rgb[2]);
       Trip yuv;
       auto& [y,u,v] = yuv;
-      y = byte(clamp (  0 + ( 299 * r + 587 * g + 114 * b) / 1000, 16,235));   // Luma clamped to MPEG scan range
+      y = byte(clamp (  0 + (    299 * r +    587 * g +    114 * b) /    1000, 16,235));   // Luma clamped to MPEG scan range
-      u = byte(clamp (128 + (-169 * r - 331 * g + 500 * b) / 1000, 0, 255));   // Chroma components mapped according to Rec.601
+      u = byte(clamp (128 + (-168736 * r - 331264 * g + 500000 * b) / 1000000, 0, 255));   // Chroma components mapped according to Rec.601
-      v = byte(clamp (128 + ( 500 * r - 419 * g -  81 * b) / 1000, 0, 255));   // (but with integer arithmetics and slightly rounded coefficients)
+      v = byte(clamp (128 + ( 500000 * r - 418688 * g -  81312 * b) / 1000000, 0, 255));   // (but with integer arithmetics and slightly rounded coefficients)
       return yuv;
     }
     
@@ -93,48 +93,59 @@ namespace node {
       frame_ = 0;
     
     if(frame_ < 1 * fps_)
-      {
+      generateNoise (buffer);
-        // create random snow...
-        for (uint i = 0; i < W*H*3; i+=3)
-          {
-            auto value = byte(rand());
-            buffer[i]   = value;
-            buffer[i+1] = value;
-            buffer[i+2] = value;
-          }
-      }
     else
-      { // create a colour strip pattern
+      generateBars (buffer);
-        typedef byte Row[W * 3];
+  }
-        
+  
-        byte* row = buffer;
+  void
-        
+  DummyImageGenerator::generateNoise (DummyFrame buffer)
-        // create a colour strip pattern in the first row...
+  {  // create random snow...
-        for (uint x = 0; x < W; ++x)
+    for (uint i = 0; i < W*H*3; i+=3)
-          {
+      {
-            byte& r = row[x*3];
+        auto value = byte(rand());
-            byte& g = row[x*3+1];
+        buffer[i]   = value;
-            byte& b = row[x*3+2];
+        buffer[i+1] = value;
-            
+        buffer[i+2] = value;
-            const byte ON = byte(0xC0);
-            const byte OFF{0};
-            
-            if     (x < 1*W/7) r = ON,  g = ON,  b = ON;
-            else if(x < 2*W/7) r = ON,  g = ON,  b = OFF;
-            else if(x < 3*W/7) r = OFF, g = ON,  b = ON;
-            else if(x < 4*W/7) r = OFF, g = ON,  b = OFF;
-            else if(x < 5*W/7) r = ON,  g = OFF, b = ON;
-            else if(x < 6*W/7) r = ON,  g = OFF, b = OFF;
-            else               r = OFF, g = OFF, b = ON;
-          }
-        
-        // fill remaining rows of the frame with the same pattern
-        for (uint y = 1; y < H; ++y)
-          memcpy(buffer + y*sizeof(Row), row, sizeof(Row));
-        
       }
   }
   
+  /** fill the RGB-Buffer with the well-known NTSC colour-bar pattern */
+  void
+  DummyImageGenerator::generateBars (DummyFrame buffer)
+  {
+    using Row = std::array<Trip, W>;
+    using Img = std::array<Row,  H>;
+    
+    Img& img = reinterpret_cast<Img&> (*buffer);
+    Row& row = img[0];
+    
+    const byte ON = byte(0xC0);
+    const byte OFF{0};
+
+    // classic NTSC colour bars  --R---G---B--
+    std::array<Trip, 7> bars = {{{ ON, ON, ON}
+                                ,{ ON, ON,OFF}
+                                ,{OFF, ON, ON}
+                                ,{OFF, ON,OFF}
+                                ,{ ON,OFF, ON}
+                                ,{ ON,OFF,OFF}
+                                ,{OFF,OFF, ON}
+                               }};
+    
+    // create a colour strip pattern in the first row...
+    for (uint x = 0; x < W; ++x)
+      {  //  quantise into 7 columns
+        uint col = x  * 7/W;
+        row[x] = bars[col];
+      }
+    
+    // fill remaining rows of the frame with the same pattern
+    for (uint y = 1; y < H; ++y)
+      img[y] = row;
+  }
+  
+  
   DummyFrame
   DummyImageGenerator::next()
   {

src/steam/engine/worker/dummy-image-generator.hpp

@@ -72,6 +72,8 @@ namespace node {
       std::array<std::byte,BUFF_SIZ> outFrame_B_;
       
       void generateFrame (DummyFrame buffer);
+      void generateNoise (DummyFrame buffer);
+      void generateBars  (DummyFrame buffer);
     };
   
   

wiki/thinkPad.ichthyo.mm

@@ -130179,21 +130179,25 @@ StM_bind(Builder<R1> b1, Extension<R1,R2> extension)
 <icon BUILTIN="idea"/>
 </node>
 </node>
-<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1746921512647" ID="ID_1654688911" MODIFIED="1746921530413" TEXT="erster Schritt: Code reorganisieren und klarer machen">
+<node COLOR="#338800" CREATED="1746921512647" ID="ID_1654688911" MODIFIED="1746971761434" TEXT="erster Schritt: Code reorganisieren und klarer machen">
-<icon BUILTIN="flag-yellow"/>
+<icon BUILTIN="button_ok"/>
 <node CREATED="1746921531585" ID="ID_156630022" MODIFIED="1746921551379" TEXT="den double-buffering-Mechanismus von der Bildgenerierung trennen"/>
-<node CREATED="1746921552092" ID="ID_492214837" MODIFIED="1746921563913" TEXT="die Farbraumkonvertierung als extra Schritt formulieren">
+<node COLOR="#338800" CREATED="1746921552092" ID="ID_492214837" MODIFIED="1746972188067" TEXT="die Farbraumkonvertierung als extra Schritt formulieren">
+<icon BUILTIN="button_ok"/>
 <node CREATED="1746921707185" ID="ID_1757569540" MODIFIED="1746921715007" TEXT="dabei auch die Theorie nochmal verifizieren">
 <node CREATED="1746921716337" ID="ID_683787640" MODIFIED="1746921728880" TEXT="&quot;yuv&quot; ist selber ein ungenauer Begriff"/>
 <node CREATED="1746921729694" ID="ID_1983082888" MODIFIED="1746921740370" TEXT="gemeint ist meist YCrCb"/>
 <node CREATED="1746929700320" ID="ID_878404124" MODIFIED="1746929714669" TEXT="die Koeffizienten sind eindeutig von Rec.601 / MPEG"/>
-<node CREATED="1746929715402" ID="ID_1228492062" MODIFIED="1746929744583" TEXT="sie sind nur vereinfacht, damit man es mit 16bit Integer-Arrithmetik machen kann"/>
+<node CREATED="1746929715402" ID="ID_1228492062" MODIFIED="1746972230168" TEXT="sie sind nur vereinfacht, damit man es mit 16bit Integer-Arrithmetik machen kann">
-</node>
+<arrowlink COLOR="#467bb9" DESTINATION="ID_1545724068" ENDARROW="Default" ENDINCLINATION="43;-21;" ID="Arrow_ID_198569523" STARTARROW="None" STARTINCLINATION="-96;5;"/>
-<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1746929753402" ID="ID_1545724068" MODIFIED="1746929764957" TEXT="da ich nun die Rechnung auf Int umstelle, k&#xf6;nnte man genauer rechnen">
-<icon BUILTIN="flag-yellow"/>
 </node>
 </node>
-<node CREATED="1746921564743" ID="ID_472874597" MODIFIED="1746921696992" TEXT="umstellen auf std::array und m&#xf6;glichst Pointer durch Referenzen ersetzen">
+<node COLOR="#338800" CREATED="1746929753402" ID="ID_1545724068" MODIFIED="1746972230168" TEXT="da ich nun die Rechnung auf Int umstelle, k&#xf6;nnte man genauer rechnen">
+<linktarget COLOR="#467bb9" DESTINATION="ID_1545724068" ENDARROW="Default" ENDINCLINATION="43;-21;" ID="Arrow_ID_198569523" SOURCE="ID_1228492062" STARTARROW="None" STARTINCLINATION="-96;5;"/>
+<icon BUILTIN="button_ok"/>
+</node>
+</node>
+<node COLOR="#338800" CREATED="1746921564743" ID="ID_472874597" MODIFIED="1746972240706" TEXT="umstellen auf std::array und m&#xf6;glichst Pointer durch Referenzen ersetzen">
 <richcontent TYPE="NOTE"><html>
   <head>
     
@@ -130205,6 +130209,7 @@ StM_bind(Builder&lt;R1&gt; b1, Extension&lt;R1,R2&gt; extension)
   </body>
 </html>
 </richcontent>
+<icon BUILTIN="button_ok"/>
 </node>
 <node COLOR="#435e98" CREATED="1746929669548" ID="ID_485365336" MODIFIED="1746936730029" TEXT="tja... compiliert aber das Ausgabeformat stimmt nicht">
 <icon BUILTIN="broken-line"/>
@@ -130230,6 +130235,9 @@ StM_bind(Builder&lt;R1&gt; b1, Extension&lt;R1,R2&gt; extension)
 </node>
 <node CREATED="1746936671244" ID="ID_1148968519" MODIFIED="1746936695084" TEXT="&#x27f9; mu&#xdf; also doch direkt nach dem Zugriff auf die Input-Daten nach int casten"/>
 </node>
+<node COLOR="#338800" CREATED="1746971763801" ID="ID_505273316" MODIFIED="1746971792732" TEXT="Auch die Generierung der Colour-Bars kann man in C++ viel eleganter formulieren">
+<icon BUILTIN="button_ok"/>
+</node>
 </node>
 </node>
 </node>