Graphics: drawImage(...,{filter:1}) added to allow smooth downscaling…

… of images

ChangeLog

@@ -38,6 +38,7 @@
             JIT: JIT failures now don't stop execution of subsequent commands - function is just executed as normal JS
             JIT: Fix scoping of JITed functions (they can now access vars in the scope they were defined in)
             Improve execution speed by not parsing strings when skipping blocks
+            Graphics: drawImage(...,{filter:1}) added to allow smooth downscaling of images
 
      2v18 : Fix drawString with setClipRect with 90/270-degree rotation (fix #2343)
             Pico/Wifi: Enabled JIT compiler

libs/graphics/jswrap_graphics.c

@@ -3112,6 +3112,7 @@ scale or angle. If `options.rotate` is set it will center images at `x,y`.
   scale : float, // the amount to scale the image up (default 1)
   frame : int    // if specified and the image has frames of data
                  //  after the initial frame, draw one of those frames from the image
+  filter : bool  // (2v19+) when set, if scale<0.75 perform 2x2 supersampling to smoothly downscale the image
 }
 ```
 
@@ -3136,6 +3137,9 @@ JsVar *jswrap_graphics_drawImage(JsVar *parent, JsVar *image, int xPos, int yPos
 
   double scale = 1, rotate = 0;
   bool centerImage = false;
+#ifndef SAVE_ON_FLASH
+  bool filter = false;
+#endif
   if (jsvIsObject(options)) {
     // support for multi-frame rendering
     int frame = jsvGetIntegerAndUnLock(jsvObjectGetChildIfExists(options,"frame"));
@@ -3147,6 +3151,9 @@ JsVar *jswrap_graphics_drawImage(JsVar *parent, JsVar *image, int xPos, int yPos
     rotate = jsvGetFloatAndUnLock(jsvObjectGetChildIfExists(options,"rotate"));
     centerImage = isfinite(rotate);
     if (!centerImage) rotate = 0;
+#ifndef SAVE_ON_FLASH
+    filter = jsvGetBoolAndUnLock(jsvObjectGetChildIfExists(options,"filter"));
+#endif
   }
 
   int x=0, y=0;
@@ -3250,7 +3257,7 @@ JsVar *jswrap_graphics_drawImage(JsVar *parent, JsVar *image, int xPos, int yPos
     } else { // handle rotation, and default to center the image
 #else
     if (true) {
-#endif
+#endif // GRAPHICS_FAST_PATHS
       GfxDrawImageLayer l;
       l.x1 = xPos;
       l.y1 = yPos;
@@ -3266,16 +3273,56 @@ JsVar *jswrap_graphics_drawImage(JsVar *parent, JsVar *image, int xPos, int yPos
       _jswrap_drawImageLayerSetStart(&l, x1, y1);
       JsGraphicsSetPixelFn setPixel = graphicsGetSetPixelFn(&gfx);
 
-      // scan across image
-      for (y = y1; y <= y2; y++) {
-        _jswrap_drawImageLayerStartX(&l);
-        for (x = x1; x <= x2 ; x++) {
-          if (_jswrap_drawImageLayerGetPixel(&l, &colData)) {
-            setPixel(&gfx, x, y, colData);
+#ifndef SAVE_ON_FLASH
+      if (filter && scale<0.75) { // 2x2 antialiasing
+        l.sx *= scale; // use scale rather than 0.5, so if scaling dithered it still works nicely
+        l.sy *= scale;
+        GfxDrawImageLayer l2;
+        memcpy(&l2, &l, sizeof(l));
+        jsvStringIteratorNew(&l2.it, l2.img.buffer, 0);
+         _jswrap_drawImageLayerNextY(&l2);
+         // scan across image
+        for (y = y1; y <= y2; y++) {
+          _jswrap_drawImageLayerStartX(&l);
+          _jswrap_drawImageLayerStartX(&l2);
+          for (x = x1; x <= x2 ; x++) {
+            uint32_t ca,cb,cc,cd;
+            bool nonTransparent = true;
+            nonTransparent &= _jswrap_drawImageLayerGetPixel(&l, &ca);
+            _jswrap_drawImageLayerNextX(&l);
+            nonTransparent &= _jswrap_drawImageLayerGetPixel(&l, &cb);
+            _jswrap_drawImageLayerNextX(&l);
+            nonTransparent &= _jswrap_drawImageLayerGetPixel(&l2, &cc);
+            _jswrap_drawImageLayerNextX(&l2);
+            nonTransparent &= _jswrap_drawImageLayerGetPixel(&l2, &cd);
+            _jswrap_drawImageLayerNextX(&l2);
+            if (true) {
+              ca = graphicsBlendColor(&gfx, ca, cb, 128);
+              cc = graphicsBlendColor(&gfx, cc, cd, 128);
+              colData = graphicsBlendColor(&gfx, ca, cc, 128);
+              setPixel(&gfx, x, y, colData);
+            }
+          }
+          _jswrap_drawImageLayerNextY(&l);
+          _jswrap_drawImageLayerNextY(&l);
+          _jswrap_drawImageLayerNextY(&l2);
+          _jswrap_drawImageLayerNextY(&l2);
+        }
+        jsvStringIteratorFree(&l2.it);
+      } else
+#endif
+      {
+        // scan across image
+        for (y = y1; y <= y2; y++) {
+          _jswrap_drawImageLayerStartX(&l);
+          for (x = x1; x <= x2 ; x++) {
+            if (_jswrap_drawImageLayerGetPixel(&l, &colData)) {
+              setPixel(&gfx, x, y, colData);
+            }
+            _jswrap_drawImageLayerNextX(&l);
           }
-          _jswrap_drawImageLayerNextX(&l);
+          _jswrap_drawImageLayerNextY(&l);
         }
-        _jswrap_drawImageLayerNextY(&l);
       }
       it = l.it; // make sure it gets freed properly
     }