KTXLoader.js 6.3 KB

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  1. import {
  2. CompressedTextureLoader
  3. } from 'three';
  4. /**
  5. * for description see https://www.khronos.org/opengles/sdk/tools/KTX/
  6. * for file layout see https://www.khronos.org/opengles/sdk/tools/KTX/file_format_spec/
  7. *
  8. * ported from https://github.com/BabylonJS/Babylon.js/blob/master/src/Misc/khronosTextureContainer.ts
  9. */
  10. class KTXLoader extends CompressedTextureLoader {
  11. constructor( manager ) {
  12. super( manager );
  13. }
  14. parse( buffer, loadMipmaps ) {
  15. const ktx = new KhronosTextureContainer( buffer, 1 );
  16. return {
  17. mipmaps: ktx.mipmaps( loadMipmaps ),
  18. width: ktx.pixelWidth,
  19. height: ktx.pixelHeight,
  20. format: ktx.glInternalFormat,
  21. isCubemap: ktx.numberOfFaces === 6,
  22. mipmapCount: ktx.numberOfMipmapLevels
  23. };
  24. }
  25. }
  26. const HEADER_LEN = 12 + ( 13 * 4 ); // identifier + header elements (not including key value meta-data pairs)
  27. // load types
  28. const COMPRESSED_2D = 0; // uses a gl.compressedTexImage2D()
  29. //const COMPRESSED_3D = 1; // uses a gl.compressedTexImage3D()
  30. //const TEX_2D = 2; // uses a gl.texImage2D()
  31. //const TEX_3D = 3; // uses a gl.texImage3D()
  32. class KhronosTextureContainer {
  33. /**
  34. * @param {ArrayBuffer} arrayBuffer- contents of the KTX container file
  35. * @param {number} facesExpected- should be either 1 or 6, based whether a cube texture or or
  36. * @param {boolean} threeDExpected- provision for indicating that data should be a 3D texture, not implemented
  37. * @param {boolean} textureArrayExpected- provision for indicating that data should be a texture array, not implemented
  38. */
  39. constructor( arrayBuffer, facesExpected /*, threeDExpected, textureArrayExpected */ ) {
  40. this.arrayBuffer = arrayBuffer;
  41. // Test that it is a ktx formatted file, based on the first 12 bytes, character representation is:
  42. // '´', 'K', 'T', 'X', ' ', '1', '1', 'ª', '\r', '\n', '\x1A', '\n'
  43. // 0xAB, 0x4B, 0x54, 0x58, 0x20, 0x31, 0x31, 0xBB, 0x0D, 0x0A, 0x1A, 0x0A
  44. const identifier = new Uint8Array( this.arrayBuffer, 0, 12 );
  45. if ( identifier[ 0 ] !== 0xAB ||
  46. identifier[ 1 ] !== 0x4B ||
  47. identifier[ 2 ] !== 0x54 ||
  48. identifier[ 3 ] !== 0x58 ||
  49. identifier[ 4 ] !== 0x20 ||
  50. identifier[ 5 ] !== 0x31 ||
  51. identifier[ 6 ] !== 0x31 ||
  52. identifier[ 7 ] !== 0xBB ||
  53. identifier[ 8 ] !== 0x0D ||
  54. identifier[ 9 ] !== 0x0A ||
  55. identifier[ 10 ] !== 0x1A ||
  56. identifier[ 11 ] !== 0x0A ) {
  57. console.error( 'texture missing KTX identifier' );
  58. return;
  59. }
  60. // load the reset of the header in native 32 bit uint
  61. const dataSize = Uint32Array.BYTES_PER_ELEMENT;
  62. const headerDataView = new DataView( this.arrayBuffer, 12, 13 * dataSize );
  63. const endianness = headerDataView.getUint32( 0, true );
  64. const littleEndian = endianness === 0x04030201;
  65. this.glType = headerDataView.getUint32( 1 * dataSize, littleEndian ); // must be 0 for compressed textures
  66. this.glTypeSize = headerDataView.getUint32( 2 * dataSize, littleEndian ); // must be 1 for compressed textures
  67. this.glFormat = headerDataView.getUint32( 3 * dataSize, littleEndian ); // must be 0 for compressed textures
  68. this.glInternalFormat = headerDataView.getUint32( 4 * dataSize, littleEndian ); // the value of arg passed to gl.compressedTexImage2D(,,x,,,,)
  69. this.glBaseInternalFormat = headerDataView.getUint32( 5 * dataSize, littleEndian ); // specify GL_RGB, GL_RGBA, GL_ALPHA, etc (un-compressed only)
  70. this.pixelWidth = headerDataView.getUint32( 6 * dataSize, littleEndian ); // level 0 value of arg passed to gl.compressedTexImage2D(,,,x,,,)
  71. this.pixelHeight = headerDataView.getUint32( 7 * dataSize, littleEndian ); // level 0 value of arg passed to gl.compressedTexImage2D(,,,,x,,)
  72. this.pixelDepth = headerDataView.getUint32( 8 * dataSize, littleEndian ); // level 0 value of arg passed to gl.compressedTexImage3D(,,,,,x,,)
  73. this.numberOfArrayElements = headerDataView.getUint32( 9 * dataSize, littleEndian ); // used for texture arrays
  74. this.numberOfFaces = headerDataView.getUint32( 10 * dataSize, littleEndian ); // used for cubemap textures, should either be 1 or 6
  75. this.numberOfMipmapLevels = headerDataView.getUint32( 11 * dataSize, littleEndian ); // number of levels; disregard possibility of 0 for compressed textures
  76. this.bytesOfKeyValueData = headerDataView.getUint32( 12 * dataSize, littleEndian ); // the amount of space after the header for meta-data
  77. // Make sure we have a compressed type. Not only reduces work, but probably better to let dev know they are not compressing.
  78. if ( this.glType !== 0 ) {
  79. console.warn( 'only compressed formats currently supported' );
  80. return;
  81. } else {
  82. // value of zero is an indication to generate mipmaps @ runtime. Not usually allowed for compressed, so disregard.
  83. this.numberOfMipmapLevels = Math.max( 1, this.numberOfMipmapLevels );
  84. }
  85. if ( this.pixelHeight === 0 || this.pixelDepth !== 0 ) {
  86. console.warn( 'only 2D textures currently supported' );
  87. return;
  88. }
  89. if ( this.numberOfArrayElements !== 0 ) {
  90. console.warn( 'texture arrays not currently supported' );
  91. return;
  92. }
  93. if ( this.numberOfFaces !== facesExpected ) {
  94. console.warn( 'number of faces expected' + facesExpected + ', but found ' + this.numberOfFaces );
  95. return;
  96. }
  97. // we now have a completely validated file, so could use existence of loadType as success
  98. // would need to make this more elaborate & adjust checks above to support more than one load type
  99. this.loadType = COMPRESSED_2D;
  100. }
  101. mipmaps( loadMipmaps ) {
  102. const mipmaps = [];
  103. // initialize width & height for level 1
  104. let dataOffset = HEADER_LEN + this.bytesOfKeyValueData;
  105. let width = this.pixelWidth;
  106. let height = this.pixelHeight;
  107. const mipmapCount = loadMipmaps ? this.numberOfMipmapLevels : 1;
  108. for ( let level = 0; level < mipmapCount; level ++ ) {
  109. const imageSize = new Int32Array( this.arrayBuffer, dataOffset, 1 )[ 0 ]; // size per face, since not supporting array cubemaps
  110. dataOffset += 4; // size of the image + 4 for the imageSize field
  111. for ( let face = 0; face < this.numberOfFaces; face ++ ) {
  112. const byteArray = new Uint8Array( this.arrayBuffer, dataOffset, imageSize );
  113. mipmaps.push( { 'data': byteArray, 'width': width, 'height': height } );
  114. dataOffset += imageSize;
  115. dataOffset += 3 - ( ( imageSize + 3 ) % 4 ); // add padding for odd sized image
  116. }
  117. width = Math.max( 1.0, width * 0.5 );
  118. height = Math.max( 1.0, height * 0.5 );
  119. }
  120. return mipmaps;
  121. }
  122. }
  123. export { KTXLoader };