@scale_layer macro with correct scale and translate (#430)

* @scale_layer macro with correct scale and translate
* bugfix in normal mapping due to clamp + tests

src/scales.jl

@@ -29,7 +29,8 @@ end
 
 function (ls::LinearScale)(x)
     if ls.clamp
-        x = clamp(x, ls.fmin, ls.fmax)
+        # clamp needs the values in low high order
+        x = clamp(x, min(ls.fmin, ls.fmax), max(ls.fmin, ls.fmax))
     end
     return (x - ls.fmin) / (ls.fmax - ls.fmin) * (ls.tmax - ls.tmin) + ls.tmin
 end
@@ -38,8 +39,9 @@ function (ls::LinearScale{T})(p::Point) where {T<:Point}
     px = p.x
     py = p.y
     if ls.clamp
-        px = clamp(px, ls.fmin.x, ls.fmax.x)
-        py = clamp(py, ls.fmin.y, ls.fmax.y)
+        # clamp needs the values in low high order
+        px = clamp(px, min(ls.fmin.x, ls.fmax.x), max(ls.fmin.x, ls.fmax.x))
+        py = clamp(py, min(ls.fmin.y, ls.fmax.y), max(ls.fmin.y, ls.fmax.y))
     end
     nx = (px - ls.fmin.x) / (ls.fmax.x - ls.fmin.x) * (ls.tmax.x - ls.tmin.x) + ls.tmin.x
     ny = (py - ls.fmin.y) / (ls.fmax.y - ls.fmin.y) * (ls.tmax.y - ls.tmin.y) + ls.tmin.y
@@ -50,15 +52,27 @@ macro scale_layer(scale_mapping, body)
     return esc(
         quote
             @layer begin
-                Luxor.translate(-$scale_mapping.fmin.x, -$scale_mapping.fmin.y)
+                # compute the center of both rectangles
+                fcenterx = ($scale_mapping.fmax.x + $scale_mapping.fmin.x) / 2
+                fcentery = ($scale_mapping.fmax.y + $scale_mapping.fmin.y) / 2
+
+                tcenterx = ($scale_mapping.tmax.x + $scale_mapping.tmin.x) / 2
+                tcentery = ($scale_mapping.tmax.y + $scale_mapping.tmin.y) / 2
+
+                # scale in x and y
                 sx =
                     ($scale_mapping.tmax.x - $scale_mapping.tmin.x) /
                     ($scale_mapping.fmax.x - $scale_mapping.fmin.x)
                 sy =
                     ($scale_mapping.tmax.y - $scale_mapping.tmin.y) /
                     ($scale_mapping.fmax.y - $scale_mapping.fmin.y)
                 Luxor.scale(sx, sy)
-                Luxor.translate($scale_mapping.tmin.x / sx, $scale_mapping.tmin.y / sy)
+
+                # translate such that inputting the center from the "from mapping" is at 0,0
+                Luxor.translate(-fcenterx, -fcentery)
+
+                # shift center of canvas to center of new region
+                Luxor.translate(tcenterx / sx, tcentery / sy)
                 $body
             end
         end,

test/animations.jl

@@ -719,7 +719,69 @@ end
     @test_logs (:error,) render(video; pathname = "test.mp3")
 end
 
-@testset "@scale_layer" begin
+@testset "@scale_layer vs mapping" begin
+    function dots_mapping(mapping, pts)
+        @JShape begin
+            @scale_layer mapping begin
+                circle.(pts, 0.1, :fill)
+            end
+        end
+    end
+
+    function dots(pts)
+        @JShape begin
+            circle.(pts, 3, :fill)
+        end
+    end
+
+    from_bls = [O, Point(1, 1), Point(-1, -1), Point(-1, 1)]
+    from_trs = [Point(10, 10), O, Point(10, 5)]
+    to_bls = [Point(10, 10), O]
+
+
+    for (from_bl, from_tr) in zip(from_bls, from_trs)
+        for to_bl in to_bls
+            diam = from_tr - from_bl
+            factor = 30
+            to_tr = to_bl + factor * diam
+            vid = Video(500, 500)
+
+            mapping = scale_linear(from_bl, from_tr, to_bl, to_tr)
+
+            nframes = 1
+            Background(1:nframes, ground)
+            dot_pos = [O]
+            Object(1:nframes, dots_mapping(mapping, dot_pos))
+
+            render(vid, tempdirectory = "images/with_mapping", pathname = "")
+
+            vid = Video(500, 500)
+
+            nframes = 1
+            Background(1:nframes, ground)
+            dot_pos = mapping.(dot_pos)
+            Object(1:nframes, dots(dot_pos))
+
+            render(vid, tempdirectory = "images/without_mapping", pathname = "")
+
+            for frame in [1]
+                png_name = lpad(string(frame), 10, "0")
+                @test_reference "images/with_mapping/$png_name.png" load(
+                    "images/without_mapping/$png_name.png",
+                )
+            end
+
+            for i in 1:1
+                rm("images/with_mapping/$(lpad(i, 10, "0")).png")
+                rm("images/without_mapping/$(lpad(i, 10, "0")).png")
+            end
+            rm("images/with_mapping/", recursive = true)
+            rm("images/without_mapping/", recursive = true)
+        end
+    end
+end
+
+@testset "@scale_layer center origin" begin
     function dots_mapping(pts)
         @JShape begin
             mapping = scale_linear(O, Point(5, 5), Point(50, -50), Point(200, -200))