feat(pixel): add imagePyramid() iterator

thi-ng · Apr 2, 2021 · 7f77e07 · 7f77e07
1 parent f6c0525
commit 7f77e07
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diff --git a/packages/pixel/src/index.ts b/packages/pixel/src/index.ts
@@ -6,6 +6,7 @@ export * from "./dither";
 export * from "./float";
 export * from "./normal-map";
 export * from "./packed";
+export * from "./pyramid";
 export * from "./sample";
 export * from "./utils";
 

diff --git a/packages/pixel/src/pyramid.ts b/packages/pixel/src/pyramid.ts
@@ -0,0 +1,31 @@
+import { assert } from "@thi.ng/api";
+import type { KernelSpec } from "./api";
+import { convolveImage, LANCZOS } from "./convolve";
+import type { FloatBuffer } from "./float";
+
+/**
+ * Yields an iterator of progressively downsampled versions of `src` (using
+ * `kernel` for filtering, default: {@link LANCZOS}(2)). Each image will be half
+ * size of the previous result, stopping only once either width or height
+ * becomes less than `minSize` (default: 1). If `includeOrig` is enabled
+ * (default), the first emitted image will be the original `src`.
+ *
+ * @param src
+ * @param kernel
+ * @param minSize
+ * @param includeOrig
+ */
+export function* imagePyramid(
+    src: FloatBuffer,
+    kernel: KernelSpec = LANCZOS(2),
+    minSize = 1,
+    includeOrig = true
+) {
+    assert(minSize > 0, `invalid min size`);
+    minSize <<= 1;
+    if (includeOrig) yield src;
+    while (src.width >= minSize && src.height >= minSize) {
+        src = convolveImage(src, { kernel, stride: 2 });
+        yield src;
+    }
+}