HTML and CSS Reference
In-Depth Information
Listing 21-1.
DDS Parsing Utility Functions
// Builds a numeric code for a given fourCC string
function fourCCToInt32(value) {
return value.charCodeAt(0) +
(value.charCodeAt(1) << 8) +
(value.charCodeAt(2) << 16) +
(value.charCodeAt(3) << 24);
}
// Turns a fourCC numeric code into a string
function int32ToFourCC(value) {
return String.fromCharCode(
value & 0xff,
(value >> 8) & 0xff,
(value >> 16) & 0xff,
(value >> 24) & 0xff
);
}
// Calcualates the size of a DXT texture level in bytes
function dxtLevelSize(width, height, bytesPerBlock) {
return ((width + 3) >> 2) * ((height + 3) >> 2) * bytesPerBlock;
}
Now let's define some constants, as shown in Listing 21-2.
Listing 21-2.
DDS Constants
// DXT formats, from:
var COMPRESSED_RGB_S3TC_DXT1_EXT = 0x83F0;
var COMPRESSED_RGBA_S3TC_DXT1_EXT = 0x83F1;
var COMPRESSED_RGBA_S3TC_DXT3_EXT = 0x83F2;
var COMPRESSED_RGBA_S3TC_DXT5_EXT = 0x83F3;
// DXT values and structures referenced from:
var DDS_MAGIC = 0x20534444;
var DDSD_MIPMAPCOUNT = 0x20000;
var DDPF_FOURCC = 0x4;
var DDS_HEADER_LENGTH = 31; // The header length in 32bit ints.
// Offsets into the header array.
var DDS_HEADER_MAGIC = 0;
var DDS_HEADER_SIZE = 1;
var DDS_HEADER_FLAGS = 2;
var DDS_HEADER_HEIGHT = 3;
var DDS_HEADER_WIDTH = 4;
var DDS_HEADER_MIPMAPCOUNT = 7;
