From a70b3c133ebb3ff897d92200b150b2db3be9d458 Mon Sep 17 00:00:00 2001
From: Karsten Schmidt <k@thi.ng>
Date: Wed, 16 Mar 2022 13:44:43 +0100
Subject: [PATCH] feat(pixel): buffer method additions, internal checks

- add FloatBuffer.premultiply/postmultiply()
- add Int/FloatBuffer.fill()
---
 packages/pixel/src/checks.ts |  4 +++
 packages/pixel/src/float.ts  | 47 ++++++++++++++++++++++++++++++++++--
 packages/pixel/src/int.ts    | 21 ++++++++++------
 3 files changed, 62 insertions(+), 10 deletions(-)

diff --git a/packages/pixel/src/checks.ts b/packages/pixel/src/checks.ts
index f6b6a3c664..68b9e1106d 100644
--- a/packages/pixel/src/checks.ts
+++ b/packages/pixel/src/checks.ts
@@ -20,3 +20,7 @@ export const ensureChannel = (fmt: IntFormat | FloatFormat, id: number) => {
 /** @internal */
 export const ensureSingleChannel = (fmt: IntFormat | FloatFormat) =>
     assert(fmt.channels.length === 1, `require single channel buffer`);
+
+/** @internal */
+export const ensureAlpha = (fmt: IntFormat | FloatFormat) =>
+    assert(!!fmt.alpha, "missing alpha channel");
diff --git a/packages/pixel/src/float.ts b/packages/pixel/src/float.ts
index e0fda56e67..26a0dba607 100644
--- a/packages/pixel/src/float.ts
+++ b/packages/pixel/src/float.ts
@@ -5,6 +5,7 @@ import { isNumber } from "@thi.ng/checks/is-number";
 import { isString } from "@thi.ng/checks/is-string";
 import { assert } from "@thi.ng/errors/assert";
 import { clamp01 } from "@thi.ng/math/interval";
+import { postmultiply, premultiply } from "@thi.ng/porter-duff/premultiply";
 import type {
     BlendFnFloat,
     BlitOpts,
@@ -61,8 +62,8 @@ export function floatBuffer(...args: any[]) {
  * @remarks
  * See {@link FloatBuffer.as} for reverse operation.
  *
- * @param src - 
- * @param fmt - 
+ * @param src -
+ * @param fmt -
  */
 export const floatBufferFromInt = (
     src: IntBuffer,
@@ -371,6 +372,44 @@ export class FloatBuffer
         return this;
     }
 
+    fill(x: NumericArray) {
+        assert(
+            x.length <= this.format.channels.length,
+            `fill value has too many channels`
+        );
+        const {
+            data,
+            stride: [stride],
+        } = this;
+        for (let i = 0, n = data.length; i < n; i += stride) {
+            data.set(x, i);
+        }
+    }
+
+    premultiply() {
+        this.ensureRGBA();
+        const {
+            data,
+            stride: [stride],
+        } = this;
+        for (let i = 0, n = data.length; i < n; i += stride) {
+            premultiply(null, data.subarray(i, i + stride));
+        }
+        return this;
+    }
+
+    postmultiply() {
+        this.ensureRGBA();
+        const {
+            data,
+            stride: [stride],
+        } = this;
+        for (let i = 0, n = data.length; i < n; i += stride) {
+            postmultiply(null, data.subarray(i, i + stride));
+        }
+        return this;
+    }
+
     clamp() {
         const data = this.data;
         for (let i = data.length; i-- > 0; ) {
@@ -479,4 +518,8 @@ export class FloatBuffer
             `dest buffer format must be same as src`
         );
     }
+
+    protected ensureRGBA() {
+        assert(this.format === FLOAT_RGBA, "require FLOAT_RGBA format");
+    }
 }
diff --git a/packages/pixel/src/int.ts b/packages/pixel/src/int.ts
index 3ca510fdc6..05589aba79 100644
--- a/packages/pixel/src/int.ts
+++ b/packages/pixel/src/int.ts
@@ -26,7 +26,7 @@ import {
     Lane,
 } from "./api.js";
 import { canvasPixels, imageCanvas } from "./canvas.js";
-import { ensureChannel, ensureSize } from "./checks.js";
+import { ensureAlpha, ensureChannel, ensureSize } from "./checks.js";
 import { ABGR8888 } from "./format/abgr8888.js";
 import { defIntFormat } from "./format/int-format.js";
 import {
@@ -72,10 +72,10 @@ export function intBuffer(...args: any[]) {
  * Creates a new pixel buffer from given HTML image element with optional
  * support for format conversion (default: {@link ABGR8888} & resizing.
  *
- * @param img - 
- * @param fmt - 
- * @param width - 
- * @param height - 
+ * @param img -
+ * @param fmt -
+ * @param width -
+ * @param height -
  */
 export const intBufferFromImage = (
     img: HTMLImageElement,
@@ -88,8 +88,8 @@ export const intBufferFromImage = (
  * Creates a new pixel buffer from given HTML canvas element with optional
  * support for format conversion (default: {@link ABGR8888}.
  *
- * @param canvas - 
- * @param fmt - 
+ * @param canvas -
+ * @param fmt -
  */
 export const intBufferFromCanvas = (
     canvas: HTMLCanvasElement,
@@ -374,6 +374,7 @@ export class IntBuffer
     }
 
     premultiply() {
+        ensureAlpha(this.format);
         __transformABGR(this.data, this.format, premultiplyInt);
         return this;
     }
@@ -402,6 +403,10 @@ export class IntBuffer
         return this;
     }
 
+    fill(x: number) {
+        this.data.fill(x);
+    }
+
     /**
      * Flips image vertically.
      */
@@ -425,7 +430,7 @@ export class IntBuffer
      * (default: `"linear"`) for interpolation. Syntax sugar for
      * {@link IntBuffer.resize}.
      *
-     * @param scale - 
+     * @param scale -
      */
     scale(scale: number, sampler: IntSampler | Filter = "linear") {
         assert(scale > 0, `scale must be > 0`);