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class Fire implements Effect {
private width: number;
private height: number;
private palette: Uint8Array = new Uint8Array(256 * 4);
private screen: Uint8Array = new Uint8Array(0);
public async init(width: number, height: number): Promise<void> {
this.width = width;
this.height = height;
this.screen = new Uint8Array(this.width * (this.height + 2));
let vOfs: number = 0;
for (let v: number = 0; v < 256; v++) {
this.palette[vOfs++] = v >> 1;
this.palette[vOfs++] = v >> 3;
this.palette[vOfs++] = v >> 4;
vOfs++;
}
}
public render(ctx: CanvasRenderingContext2D, _: number): void {
const dest: ImageData = ctx.getImageData(0, 0, this.width, this.height);
let ofs: number = 0;
// average screen
for (; ofs < this.width * this.height; ofs++) {
const y1: number = (this.screen[ofs + this.width - 1] +
this.screen[ofs + this.width]) >> 1;
const y2: number = (this.screen[ofs + this.width * 2] +
this.screen[ofs + this.width * 2 + 1]) >> 1;
this.screen[ofs] = Math.max(((y1 + y2) >> 1) - 2, 0);
}
// generate new lines
for (; ofs < this.width * (this.height + 2); ofs++) {
this.screen[ofs] = Math.random() > 0.5 ? 255 : 0;
}
// and output
ofs = 0;
for (let destOfs: number = 0; destOfs < this.width * this.height * 4;) {
let pix: number = this.screen[ofs++] * 4;
dest.data[destOfs++] = this.palette[pix++];
dest.data[destOfs++] = this.palette[pix++];
dest.data[destOfs++] = this.palette[pix++];
dest.data[destOfs++] = 0xff;
}
ctx.putImageData(dest, 0, 0);
}
}
demoFX.register("fire", new Fire());