nes-emu/ppu/registers/PPUMask.js

A NES emulator

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _registers = require("../../registers");
/**
 * PPU Mask Register (> write)
 *
 * Controls the rendering of sprites and backgrounds, as well as colour effects.
 */
class PPUMask extends _registers.WriteOnlyInMemoryRegister {
  constructor() {
    super();
    this.addReadOnlyField("grayscale", 0).addReadOnlyField("showBackgroundInLeftmost8PixelsOfScreen", 1).addReadOnlyField("showSpritesInLeftmost8PixelsOfScreen", 2).addReadOnlyField("showBackground", 3).addReadOnlyField("showSprites", 4).addReadOnlyField("emphasizeRed", 5).addReadOnlyField("emphasizeGreen", 6).addReadOnlyField("emphasizeBlue", 7);
  }

  /** Transforms a BGR `color` following the register's rules (grayscale or emphasize bits). */
  transform(color) {
    let r = color >> 0 & 0xff;
    let g = color >> 8 & 0xff;
    let b = color >> 16 & 0xff;
    if (this.grayscale) {
      const gray = Math.floor(r / 3) + Math.floor(g / 3) + Math.floor(b / 3);
      r = gray;
      g = gray;
      b = gray;
    }
    if (this.emphasizeRed || this.emphasizeGreen || this.emphasizeBlue) {
      const all = this.emphasizeRed && this.emphasizeGreen && this.emphasizeBlue;
      r = this.emphasizeRed && !all ? r : Math.floor(r * 0.75);
      g = this.emphasizeGreen && !all ? g : Math.floor(g * 0.75);
      b = this.emphasizeBlue && !all ? b : Math.floor(b * 0.75);
    }
    return r << 0 | g << 8 | b << 16;
  }

  /** Returns whether any rendering (background or sprites) is active or not. */
  get isRenderingEnabled() {
    return this.showBackground || this.showSprites;
  }
}
exports.default = PPUMask;