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Overview
| Artifact ID: | 679c39fb290a17aab3c11b3266d81efec04d2496 |
|---|---|
| Page Name: | reference_table |
| Date: | 2014-07-29 16:02:53 |
| Original User: | sandro |
| Parent: | 0737b4eff56e9dd7f1ccc1b2770f1cf52ab15e7c (diff) |
| Next | 5f8d10535f0868089e8b3eb6df55a7a4badbaaf9 |
Content
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Supported sample types
| Family | Bits | Mnemonic | Notes | ||
|---|---|---|---|---|---|
| Unsigned Integer | 1 | 1-BIT |
| ||
| 2 | 2-BIT |
| |||
| 4 | 4-BIT |
| |||
| 8 | UINT8 |
| |||
| 16 | UINT16 |
| |||
| 32 | UINT32 |
| |||
| Signed Integer | 8 | INT8 |
| ||
| 16 | INT16 |
| |||
| 32 | INT32 |
| |||
| Floating Point | 32 | FLOAT |
| ||
| 64 | DOUBLE |
|
Supported pixel types
| Mnemonic | Bands | Sample type | Notes |
|---|---|---|---|
| MONOCHROME | 1 | 1-BIT | the implicit photometric interpretation always is:
|
| PALETTE | 1 | 1-BIT 2-BIT 4-BIT UINT8 |
the implicit photometric interpretation is always the one defined by the Palette Color associated to the Raster Coverage. This actually corresponds to an RGB output image, the color of each pixel being indirectly determined by its palette index. |
| GRAYSCALE | 1 | 2-BIT 4-BIT UINT8 |
the implicit photometric interpretation is always of the Grayscale type. 0 always corresponds to full black, and the max value to full white. |
| RGB | 3 | UINT8 UINT16 |
the implicit photometric interpretation is always of the RGB type. |
| MULTIBAND | > 1 < 256 |
UINT8 UINT16 |
there is no implicit photometric interpretation. |
| DATAGRID | 1 | INT8 UINT8 INT16 UINT16 INT32 UINT32 FLOAT DOUBLE |
there is no implicit photometric interpretation. |
Supported compression algorithms
| Mnemonic | Compression type | Notes |
|---|---|---|
| NONE | lossless | no compression at all: simply an array of tightly packed values. |
| DEFLATE | lossless | a general purpose compression algorithm used by ZIP archives and implemented by zlib. You can find more detailed information about this algorithm here. |
| LZMA | lossless | an advanced general purpose compression algorithm used by 7-ZIP archives and implemented by liblzma. You can find more detailed information about this algorithm here. Please note: this algorithm is very slow while compressing, but is reasonably fast while decompressing; and usually ensures better compression ratios than DEFLATE. |
| FAX4 | lossless | an highly specialized compression algorithm only supporting monochrome images initially developed for fax machines: implemented by libtiff. You can find more detailed information about this algorithm here. |
| PNG | lossless | a very popular general purpose image format supporting RGB, Grayscale and Palette-based colorspaces and fully supporting transparencies. Implemented by libpng. You can find more detailed information about this compressed format here. |
| JPEG | lossy | an universally spread photographic image format supporting RGB and Grayscale colorspaces but completely lacking of any transparency support. Implemented by libjpeg. You can find more detailed information about this compressed format here. |
| WEBP | lossy | an innovative photographic image format supporting RGB and Grayscale colorspaces and fully supporting transparencies. Implemented by libwebp. You can find more detailed information about this compressed format here. Please note: this algorithm is very slow while compressing, but is reasonably fast while decompressing; and usually ensures slightly better compression ratios than JPEG at the same quality level. |
| LL_WEBP | lossless | exactly the same of the previous one, but in lossless mode. This usually means accepting very low compression ratios (about 1:2). |
Pixel / Sample / Compression compatibility chart
| MONOCHROME | PALETTE | GRAYSCALE | RGB | MULTIBAND | DATAGRID | ||
|---|---|---|---|---|---|---|---|
| 1-BIT | 1-BIT 2-BIT 4-BIT UINT8 |
2-BIT 4-BIT UINT8 for Grayscale 16bit please see: DATAGRID UINT16 |
UINT8 | UINT16 | UINT8 UINT16 |
INT8 UINT8 INT16 UINT16 INT32 UINT32 FLOAT DOUBLE | |
| NONE | yes | yes | yes | yes | yes | yes | yes |
| DEFLATE | yes | yes | yes | ||||
| LZMA | yes | yes | yes | ||||
| FAX4 | yes | ||||||
| PNG | yes | yes | yes | yes | |||
| JPEG | yes | yes | |||||
| WEBP | yes | yes | |||||
| LL_WEBP | yes | yes | |||||
Multi-resolution Pyramid levels configuration
| Pixel type | Base level full resolution | Upper levels rescaled | Notes |
|---|---|---|---|
| MONOCHROME | 1-BIT | GRAYSCALE UINT8 compression PNG | applying an high-quality halftone interpolation rescaling/downsampling algorithm ensures a better visual quality but imposes a change in color model. |
| PALETTE | 1-BIT | RGB UINT8 compression PNG | same as above |
| 2-BIT | RGB UINT8 compression PNG | same as above | |
| 4-BIT | RGB UINT8 compression PNG | same as above | |
| UINT8 | RGB UINT8 compression JPEG | same as above | |
| GRAYSCALE | 2-BIT | GRAYSCALE UINT8 compression JPEG | same as above |
| 4-BIT | GRAYSCALE UINT8 compression JPEG | same as above | |
| UINT8 | GRAYSCALE UINT8 compression JPEG | ||
| RGB | UINT8 | RGB UINT8 compression JPEG | |
| UINT16 | RGB UINT16 compression DEFLATE | ||
| MULTIBAND | UINT8 | MULTIBAND UINT8 compression DEFLATE | |
| UINT16 | MULTIBAND UINT16 compression DEFLATE | ||
| DATAGRID | INT8 | MULTIBAND INT8 compression DEFLATE | |
| UINT8 | MULTIBAND UINT8 compression DEFLATE | ||
| INT16 | MULTIBAND INT16 compression DEFLATE | ||
| UINT16 | MULTIBAND UINT16 compression DEFLATE | ||
| INT32 | MULTIBAND INT32 compression DEFLATE | ||
| UINT32 | MULTIBAND UINT32 compression DEFLATE | ||
| FLOAT | MULTIBAND FLOAT compression DEFLATE | ||
| DOUBLE | MULTIBAND DOUBLE compression DEFLATE |
- the same identical PixelType and SampleType are adopted for both base-level and upper rescaled-levels whenever is possible.
- except when a change in the color space is strictly required by high-quality rescaling/downsampling algorithm supporting halftone interpolation.
- all upper Pyramid levels (rescaled) are always implicitly compressed: these are always heavily reworked levels, so there is any real need to carefully preserve all input data exactly as they originally were.
- JPEG is used for either RGB and GRAYSCALE (UINT8).
- PNG is used for all limited extension samples: 1-BIT, 2-BIT and 4-bit.
All these samples could implicitly imply transparency, and only PNG will offer an adequate support. - DEFLATE is used for any other configuration.
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