The magnifyBy2 fix.

src/pixie/images.nim

@@ -653,16 +653,22 @@ proc drawUber(
     p = matInv * vec2(0 + h, 0 + h)
     dx = matInv * vec2(1 + h, 0 + h) - p
     dy = matInv * vec2(0 + h, 1 + h) - p
-    minFilterBy2 = max(dx.length, dy.length)
+    filterBy2 = max(dx.length, dy.length)
     b = b
 
-  while minFilterBy2 >= 2.0:
+  while filterBy2 >= 2.0:
     b = b.minifyBy2()
     p /= 2
     dx /= 2
     dy /= 2
-    minFilterBy2 /= 2
-    matInv = matInv * scale(vec2(0.5, 0.5))
+    filterBy2 /= 2
+
+  while filterBy2 <= 0.5:
+    b = b.magnifyBy2()
+    p *= 2
+    dx *= 2
+    dy *= 2
+    filterBy2 *= 2
 
   let smooth = not(
     dx.length == 1.0 and

tests/test_images_draw.nim

@@ -151,7 +151,7 @@ block:
     b = newImage(50, 50)
   a.fill(rgba(255, 255, 255, 255))
   b.fill(rgbx(0, 0, 0, 255))
-  a.draw(b, translate(vec2(14.64, 50.4)) * rotate(45.toRadians))
+  a.draw(b, translate(vec2(0, 50)) * rotate(45.toRadians))
   doDiff(a, "smooth2")
 
 block:
@@ -226,3 +226,14 @@ block:
   let m = translate(vec2(0.5, 0.5)) * scale(vec2(2, 2))
   a.draw(b, m)
   doDiff(a, "smooth10")
+
+block:
+  let
+    a = newImage(100, 100)
+    b = readImage(&"tests/images/turtle.png")
+  a.fill(rgba(255, 255, 255, 255))
+  let m = translate(vec2(-43.29, -103.87)) *
+    rotate(-15.toRadians) *
+    scale(vec2(263.86/40, 263.86/40))
+  a.draw(b, m)
+  doDiff(a, "smooth11")