first go at generic resize_bitmap() for NCCSCALE_INFLATE #1576

src/lib/visual.c

@@ -1063,8 +1063,48 @@ int ncvisual_resize(ncvisual* nc, int rows, int cols){
   return 0;
 }
 
+// naive resize of |bmap| from |srows|x|scols| -> |drows|x|dcols|, suitable for
+// pixel art. we either select at a constant interval (for shrinking) or duplicate
+// at a constant ratio (for inflation). in the absence of a multimedia engine, this
+// is the only kind of resizing we support.
+static inline uint32_t*
+resize_bitmap(const uint32_t* bmap, int srows, int scols, size_t sstride,
+              int drows, int dcols, size_t dstride){
+  if(sstride < scols * sizeof(*bmap)){
+    return NULL;
+  }
+  if(dstride < dcols * sizeof(*bmap)){
+    return NULL;
+  }
+  size_t size = drows * dstride;
+  uint32_t* ret = malloc(size);
+  if(ret == NULL){
+    return NULL;
+  }
+  float xrat = (float)dcols / scols;
+  float yrat = (float)drows / srows;
+fprintf(stderr, "xrat: %f yrat: %f\n", xrat, yrat);
+  int dy = 0;
+  for(int y = 0 ; y < srows ; ++y){
+    float ytarg = y * yrat;
+    while(ytarg > dy){
+      int dx = 0;
+      for(int x = 0 ; x < scols ; ++x){
+        float xtarg = x * xrat;
+        while(xtarg > dx){
+          ret[dy * dstride / sizeof(*ret) + dx] = bmap[y * sstride / sizeof(*ret) + x];
+          ++dx;
+        }
+      }
+    }
+    ++dy;
+  }
+  return ret;
+}
+
 // Inflate each pixel of 'bmap' to 'scale'x'scale' pixels square, using the
 // same color as the original pixel.
+// FIXME replace with resize_bitmap()
 static inline void*
 inflate_bitmap(const uint32_t* bmap, int scale, int rows, int stride, int cols){
   size_t size = rows * cols * scale * scale * sizeof(*bmap);