What is .dds file?

Direct Draw Surface is a raster image. It was created by Microsoft in 1999.
Images are compressed.
File extension is .dds.

Software handling .dds files

Rest7 Free Online Converter

Structure of .dds images

Name	Type	Description
Magic	Char8[4]	"DDS" + #20
Size	UInt32	Must be 124
Flags	UInt32	Possible bit values: #1 = DDSD_CAPS #2 = DDSD_HEIGHT #4 = DDSD_WIDTH #8 = DDSD_PITCH #1000 = DDSD_PIXELFORMAT #20000 = DDSD_MIPMAPCOUNT #80000 = DDSD_LINEARSIZE #800000 = DDSD_DEPTH
Height	UInt32
Width	UInt32
Pitch Or Linear Size	UInt32	pitch or number of bytes per scan line in an uncompressed image
Depth	UInt32	depth of a volume texture in pixels
Mip Map Count	UInt32	Number of mipmap levels,
Reserved1	UInt32[11]	Unused
Pixel Format Size	UInt32	Always 32
Pixel Format Flags	UInt32	Possible bit values: #1 = DDPF_ALPHAPIXELS - texture contains alpha data #2 = DDPF_ALPHA - used in older DDS files for alpha #4 = DDPF_FOURCC -texture contains compressed RGB #40 = DDPF_RGB - texture contains uncompressed RGB #200 = DDPF_YUV - used in older DDS files for uncompressed YUV #20000 = DDPF_LUMINANCE - used in older DDS files for uncompressed color single channel
Pixel Format FourCC	Char8[4]	Possible values: "DXT1", "DXT2", "DXT3", "DXT4" or "DXT5"
Pixel Format RGB Bit Count	UInt32	number of bits in RGB
Pixel Format R Bit Mask	UInt32	Red (or Y) mask for color data. In A8R8G8B8 format the red mask would be #00FF0000
Pixel Format G Bit Mask	UInt32	Green (or U) mask for color data. In A8R8G8B8 format the green mask would be #0000FF00
Pixel Format B Bit Mask	UInt32	Blue (or V) mask for color data. In A8R8G8B8 format the blue mask would be #000000FF
Pixel Format A Bit Mask	UInt32	Alpha mask for alpha data. In A8R8G8B8 format the alpha mask would be #FF000000
Caps	UInt32	Possible bit values: #8 = DDSCAPS_COMPLEX - used on any file that contains more than one surface (eg. mipmap, cubic environment map) #400000 = DDSCAPS_MIPMAP - should be used for a mipmap #1000 = DDSCAPS_TEXTURE
Caps2	UInt32	Possible bit values: #200 - DDSCAPS2_CUBEMAP - required for a cube map #400 - DDSCAPS2_CUBEMAP_POSITIVEX - required when these surfaces are stored in a cube map #800 - DDSCAPS2_CUBEMAP_NEGATIVEX - required when these surfaces are stored in a cube map #1000 - DDSCAPS2_CUBEMAP_POSITIVEY - required when these surfaces are stored in a cube map #2000 - DDSCAPS2_CUBEMAP_NEGATIVEY - required when these surfaces are stored in a cube map #4000 - DDSCAPS2_CUBEMAP_POSITIVEZ - required when these surfaces are stored in a cube map #8000 - DDSCAPS2_CUBEMAP_NEGATIVEZ - required when these surfaces are stored in a cube map #200000 - DDSCAPS2_VOLUME - required for a volume texture
Caps3	UInt32	Unused
Caps4	UInt32	Unused
Reserved2	UInt32	Unused

Specification of .ext ?> file

Microsft MSDN
Data types:
UInt8, UInt16, UInt32, UInt64 - Unsigned Integer 8 bit, 16 bit, 32 bit, 64 bit
Int8, Int16, Int32, Int64 - Signed Integer 8 bit, 16 bit, 32 bit, 64 bit
UMint16, UMint32 - Unsigned Motorola Integer 16 bit, 32 bit (Big Endian)
Char8, Char16 - Char 8 bit, 16 bit

Real world .dds samples

If you have graphics of this type, please upload them below: