textureBuilder.ts

import * as structs                                                          from '../const/structs'
import { NF_MASKED, PALETTE_SIZE, PALETTE_ALPHA_INDEX, RGB_SIZE, RGBA_SIZE } from '../const/constants'

/**
 * Build texture data from buffer
 * @param buffer The model buffer
 * @param texture Texture description
 * @returns Uint8ClampedArray with unpacked RGBA data of a texture
 */
export const buildTexture = (buffer: ArrayBuffer, texture: structs.Texture): Uint8ClampedArray => {
  const textureArea: number = texture.width * texture.height
  const isTextureMasked: number = texture.flags & NF_MASKED

  const textureData = new Uint8Array(buffer, texture.index, textureArea)

  // Palette of colors
  const palette = new Uint8Array(buffer, texture.index + textureArea, PALETTE_SIZE)

  // RGB color which will be replaced with transparency
  const alphaColor: Uint8Array = palette.slice(PALETTE_ALPHA_INDEX, PALETTE_ALPHA_INDEX + RGB_SIZE)

  // Create new image buffer
  const imageBuffer = new Uint8ClampedArray(textureArea * RGBA_SIZE)

  // Parsing indexed color: every item in texture data is index of color in
  // colors palette
  for (let i = 0; i < textureData.length; i++) {
    const item = textureData[i]

    const paletteOffset = item * RGB_SIZE
    const pixelOffset = i * RGBA_SIZE

    // Checks is alpha color
    const isAlphaColor
      = palette[paletteOffset + 0] === alphaColor[0]
      && palette[paletteOffset + 1] === alphaColor[1]
      && palette[paletteOffset + 2] === alphaColor[2]

    if (isTextureMasked && isAlphaColor) {
      // This modifies the model's data. Sets the mask color to black.
      // This is also done by Jed's model viewer (export texture has black)
      imageBuffer[pixelOffset + 0] = 0 // red
      imageBuffer[pixelOffset + 1] = 0 // green
      imageBuffer[pixelOffset + 2] = 0 // blue
      imageBuffer[pixelOffset + 3] = 0 // alpha
    } else {
      // Just applying to texture image data
      imageBuffer[pixelOffset + 0] = palette[paletteOffset + 0] // red
      imageBuffer[pixelOffset + 1] = palette[paletteOffset + 1] // green
      imageBuffer[pixelOffset + 2] = palette[paletteOffset + 2] // blue
      imageBuffer[pixelOffset + 3] = 255 // alpha
    }
  }

  return imageBuffer
}