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msagent.js/core: Rewrite imageDrawToBuffer()

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Now rows are not read and it doesn't use a BufferStream at all. Probably inconsequential for performance or memory usage but it's a cleaner way to implement it.
This commit is contained in:
Lily Tsuru 2024-11-25 17:27:48 -05:00
parent 02a26109c0
commit 883ef7357c
1 changed files with 6 additions and 21 deletions
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27
msagent.js/core/src/image.ts
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@ -1,4 +1,5 @@
import { AcsImageEntry } from './structs/image';
import { RGBAColor } from './structs/core';
// probably should be in a utility module
function dwAlign(off: number): number {
@ -10,9 +11,6 @@ function dwAlign(off: number): number {
return ul;
}
import { BufferStream, SeekDir } from './buffer';
import { RGBAColor } from './structs/core';
/// Draws an ACS image to a newly allocated buffer.
/// This function normalizes the agent 8bpp DIB format to a saner RGBA format,
/// that can be directly converted to an ImageData for drawing to a web canvas.
@ -20,30 +18,17 @@ import { RGBAColor } from './structs/core';
/// However, that should be done (and is done) by a higher level web layer.
export function imageDrawToBuffer(imageEntry: AcsImageEntry, palette: RGBAColor[]) {
let rgbaBuffer = new Uint32Array(imageEntry.image.width * imageEntry.image.height);
let buffer = imageEntry.image.data;
let bufStream = new BufferStream(buffer);
let rows = new Array<Uint8Array>(imageEntry.image.height - 1);
// Read all the rows bottom-up first. This idiosyncracy is due to the fact
// that the bitmap data is actually formatted to be used as a GDI DIB
// (device-independent bitmap), so it inherits all the strange baggage from that.
for (let y = imageEntry.image.height - 1; y >= 0; --y) {
let row = bufStream.subBuffer(imageEntry.image.width).raw();
rows[y] = row.slice(0, imageEntry.image.width);
// Seek to the next DWORD aligned spot to get to the next row.
// For most images this may mean not seeking at all.
bufStream.seek(dwAlign(bufStream.tell()), SeekDir.BEG);
}
// Next, draw the rows converted to RGBA, top down (so it's drawn correctly,
// and in the RGBA format we want to return)
for (let y = 0; y < imageEntry.image.height - 1; ++y) {
let row = rows[y];
// flip y so it's all top down properly
let yy = imageEntry.image.height - 1 - y;
let rowStartOffset = yy * dwAlign(imageEntry.image.width);
for (let x = 0; x < imageEntry.image.width; ++x) {
rgbaBuffer[y * imageEntry.image.width + x] = palette[row[x]].to_rgba();
rgbaBuffer[y * imageEntry.image.width + x] = palette[buffer[rowStartOffset + x]].to_rgba();
}
}
return rgbaBuffer;