Image Options Section

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For image datasets, the following options can be set:

Texture format: Defines the texture compression format. The default setting is RGBA_DXT3, which produces acceptable results in terms of data size and quality for most applications.

RGBA_8888: 32 Bit uncompressed color. The best image quality but the most storage space is needed.

RGBA_5551: 16 Bit uncompressed color, 5 Bit per color channel and 1 Bit for transparency. Only half the storage space is needed but the image quality is greatly reduced. Suitable for images with fewer colors, like pixel maps for example.

RGBA_DXT1/3/5: The color data is compressed according to the DXT codec specification. These formats are supported by most modern graphics hardware and consume less space on disk and texture memory while providing acceptable image quality.

DXT1 compresses the color data the most (8:1 compared to RGBA_8888) but cannot handle transparency well. The quality of the resulting textures will be rather poor for aerial imagery but might be still acceptable for pixel maps.

DXT3 and DXT5 both compress the color data with a factor of 4:1 (compared to RGBA_8888), resulting in better image quality. DXT5 handles transparency better which might be necessary in some cases.

Tile size: The texture size of a tile. The default setting is 256 x 256.
For the “combined” storage method, the tile size influences the number of files generated (512 x 512 will produce only about 1/4th the number of files, whereas 128 x 128 will produce 4 times as many).
Smaller tiles are better for web streaming purposes but produce more overhead while rendering and more seams become evident when the maximum level of detail is reached.

Mask color: If this color appears in the raw data, it will be interpreted as “100% transparent” or “no data”. This color must be set to the color used in the raw data for masking.