Add spec file for interpolate

spec/interpolate_spec.lua

@@ -0,0 +1,44 @@
+local vips = require "vips"
+
+-- test image interpolation
+describe("image interpolation", function()
+    setup(function()
+        -- vips.log.enable(true)
+    end)
+
+    it("can rotate an image using nearest interpolator", function()
+        local interpolate = vips.Interpolate.new_from_name("nearest")
+        local original = {
+            { 1,  2,  3,  4,  5,  6,  7 },
+            { 8,  9,  10, 11, 12, 13, 14 },
+            { 15, 16, 17, 18, 19, 20, 21 },
+            { 22, 23, 24, 25, 26, 27, 28 },
+            { 29, 30, 31, 32, 33, 34, 35 },
+            { 36, 37, 38, 39, 40, 41, 42 },
+            { 43, 44, 45, 46, 47, 48, 49 },
+        }
+        local rotated = {
+            { 0.0, 0.0,  0.0,  0.0,  0.0,  1.0,  0.0,  0.0,  0.0,  0.0 },
+            { 0.0, 0.0,  0.0,  0.0,  0.0,  1.0,  2.0,  0.0,  0.0,  0.0 },
+            { 0.0, 0.0,  0.0,  0.0,  15.0, 9.0,  3.0,  3.0,  0.0,  0.0 },
+            { 0.0, 0.0,  0.0,  22.0, 16.0, 17.0, 10.0, 4.0,  5.0,  0.0 },
+            { 0.0, 0.0,  29.0, 30.0, 24.0, 17.0, 18.0, 12.0, 5.0,  6.0 },
+            { 0.0, 43.0, 37.0, 31.0, 31.0, 25.0, 19.0, 19.0, 13.0, 7.0 },
+            { 0.0, 0.0,  45.0, 38.0, 32.0, 33.0, 26.0, 20.0, 21.0, 0.0 },
+            { 0.0, 0.0,  0.0,  46.0, 40.0, 33.0, 34.0, 28.0, 0.0,  0.0 },
+            { 0.0, 0.0,  0.0,  0.0,  47.0, 41.0, 35.0, 0.0,  0.0,  0.0 },
+            { 0.0, 0.0,  0.0,  0.0,  0.0,  49.0, 0.0,  0.0,  0.0,  0.0 },
+        }
+        local im = vips.Image.new_from_array(original)
+        local rot = im:rotate(45, { interpolate = interpolate })
+        local rotcheck = vips.Image.new_from_array(rotated)
+        assert.are.equal(rot:width(), 10)
+        assert.are.equal(rot:height(), 10)
+        assert.are.equal(rot:bands(), 1)
+        for x = 1, 10 do
+            for y = 1, 10 do
+                assert.are_equal(rot(x - 1, y - 1), rotcheck(x - 1, y - 1))
+            end
+        end
+    end)
+end)