transform uses prepareUpdate

src/xdim.js

@@ -481,12 +481,19 @@ function iterPoints({ order, sizes, rect = {} }) {
   });
 }
 
-function transform({ data, fill, from, to, sizes, useLayoutCache = true }) {
+function transform({ data, fill = undefined, from, to, sizes, useLayoutCache = true }) {
   if (typeof from === "string") from = parse(from, { useLayoutCache });
   if (typeof to === "string") to = parse(to, { useLayoutCache });
 
   const { data: out_data } = prepareData({ fill, layout: to, sizes });
 
+  const update = prepareUpdate({
+    useLayoutCache,
+    data: out_data,
+    layout: to,
+    sizes
+  });
+
   const points = iterPoints({ sizes });
 
   for (point of points) {
@@ -499,10 +506,7 @@ function transform({ data, fill, from, to, sizes, useLayoutCache = true }) {
 
     // insert into new frame
     update({
-      data: out_data,
-      layout: to,
       point,
-      sizes,
       value
     });
   }

tests/perf.js

@@ -1,5 +1,5 @@
 const test = require("flug");
-const { prepareData, prepareSelect, select, update, prepareUpdate } = require("../src/xdim");
+const { prepareData, prepareSelect, select, update, prepareUpdate, transform } = require("../src/xdim");
 
 const sizes = { a: 4, b: 1e3, c: 1e3 };
 const layout = "[a][b][c]";
@@ -83,3 +83,14 @@ test("perf: prepareUpdate [band][row,column]", ({ eq }) => {
   }
   console.timeEnd("perf: prepareUpdate [band][row,column]");
 });
+
+test("perf: transform [band][row,column] to [row,column,band]", ({ eq }) => {
+  console.time("perf: transform [band][row,column] to [row,column,band]");
+  transform({
+    data,
+    from: im_layout,
+    to: "[row,column,band]",
+    sizes: im_sizes
+  });
+  console.timeEnd("perf: transform [band][row,column] to [row,column,band]");
+});