Supported Image Formats
Carmenta Engine can read a large number of different raster formats through the various data set classes; see Working with Raster Data for an introduction. But there are also a few commonly used image formats that are supported directly by for instance the RasterSymbol class, and through methods like Raster.FromFile:
Image format name | Recognized file extension |
|---|---|
CompuServe Graphics Interchange Format, GIF | .gif |
Tagged Image File Format, TIFF | .tif or .tiff |
Portable Network Graphics, PNG | .png |
JPEG | .jpg, .jpeg or .jif |
Windows Bitmap, BMP | .bmp |
WebP | .webp |
TrueVision TGA (TARGA) | .tga |
Silicon Graphics IRIS Image | .rgb, .rgba, .sgi and .bw |
These image formats are also supported for writing, using for instance methods Raster.Save or Drawable.Save. Images may also be read from or written to memory buffers instead of files, with methods like Raster.FromStream or Raster.GetImage.
The support for reading and writing these formats is also used by the ImageDataSet class. However, ImageDataSet adds a lot of additional functionality, dealing with for instance georeferencing, tiling, and low-resolution overviews.
The following paragraphs describe in more detail the Carmenta Engine read and write support for the different formats.
GIF
Read support
Can read most GIF variants.
Animated GIFs are not supported
Write support
Can write 8-bit GIF87a and GIF89a images.
Can write transparent colors.
Always writes non-interlaced.
For Carmenta Engine methods accepting an options parameter, the following options can be specified when writing GIF:
Attribute | Values | Default | Comment |
|---|---|---|---|
transparent | 0 or 1 | 0 (off) | Make background transparent (forces GIF89a). |
TIFF
Read support
Can read most TIFF and GeoTIFF variants.
ImageDataSet can read georeferencing information such as coordinate reference system and bounds from GeoTIFF tags.
Can read single-band images types with 1, 2, 4, 8, 16 or 32 bit integers, or 32 bit float values, with or without color tables. 64-bit double rasters can also be read, but the values will be truncated to 32-bit floats.
Can read multi-band RGB, RGBA, CMYK and YCbCr images.
PackBits, LZW and JPEG compression schemes can be used.
Internal tiling and striping is supported.
ImageDataSet can use overview images stored in the same file, or in a separate .ovr file.
Can read transparency masks stored in the same file, or in a separate .msk file.
Write support
Carmenta Engine methods accepting georeferencing information will write GeoTIFF images, with embedded tags specifying bounds and/or coordinate reference system information. Methods without such information will create regular TIFF images. The format of the source raster is used to determine whether the resulting images are saved as RGB or RGBA images. If a color table is specified it will result in an image with a palette.
For Carmenta Engine methods accepting an options parameter, the following options can be specified for TIFF:
Attribute | Values | Default | Comment |
|---|---|---|---|
compression | 0 or 5 | 5 (LZW) | Compression algorithm. 0 means no compression at all. 5 means LZW (Lempel-Ziv-Welch) compression. |
resolution | Raster resolution in pixels per inch. | 96 | Sets the X and Y raster resolution fields in the generated TIFF file. This value has no geographical meaning. |
tileSize | 16, 32, etc. | 0 (off) | tileSize must be a multiple of 16 and the width and height of the image must be evenly divisible by tileSize. |
PNG
Read support
Can read most PNG variants.
Write support
Can write color table, RGB and RGBA images.
Can write transparent colors.
For Carmenta Engine methods accepting an options parameter, the following options can be specified for PNG:
Attribute | Values | Default | Comment |
|---|---|---|---|
transparent | 0 or 1 | 0 (off) | Make background transparent. |
force8bit | 0 or 1 | 0 (off) | Writes RGB and RGBA rasters as 8-bit color-table PNG files. |
compression | 0 to 9 | 6 | Controls PNG compression level. A higher value gives better compression, but is also slower. 0 means no compression at all. |
JPEG
Read support
Can read most JPEG variants.
Cannot read JPEG stored with YCCK or CMYK color spaces.
Write support
Always writes non-progressive.
Rasters with color tables are converted to RGB when written.
For Carmenta Engine methods accepting an options parameter, the following options can be specified for JPEG:
Attribute | Values | Default | Comment |
|---|---|---|---|
quality | 1 to 100 | 75 | Image quality. |
BMP
Read support
Can read 1, 4, 8 and 24 bit BMP images.
Compressed files are not supported.
Write support
Can write 24 bit uncompressed images. Other bit depths are converted to 24 bit.
WebP
Read support
Can read most WebP images.
Animated WebP images are not supported.
Write support
Rasters with color tables are converted to RGB or RGBA when written.
Can write lossy or lossless WebP images.
For Carmenta Engine methods accepting an options parameter, the following options can be specified for WebP:
Attribute | Values | Default | Comment |
|---|---|---|---|
transparent | 0 or 1 | 0 (off) | Make background transparent. |
quality | 0 to 100 | 100 | Image quality. If a value above 100 is specified, the image will be saved in a lossless WebP format. |
TrueVision TGA (TARGA)
Read support
Can read TGA version 2.0 images.
Write support
Rasters with color tables are converted to RGB or RGBA when written.
For Carmenta Engine methods accepting an options parameter, the following options can be specified for TGA:
Attribute | Values | Default | Comment |
|---|---|---|---|
transparent | 0 or 1 | 0 (off) | Make background transparent. |
SGI Image File Format
Read Support
Can read 1, 2, 3 and 4 channel images as gray, gray with alpha, RGB and RGBA images respectively.
Supports reading with and without RLE compression.
Reads 2 bytes per channel data as 1 byte per channel.
Write support
Rasters with color tables are converted to RGB or RGBA when written.
Only uncompressed writing is supported.
For Carmenta Engine methods accepting an options parameter, the following options can be specified for RGB:
Attribute | Values | Default | Comment |
|---|---|---|---|
transparent | 0 or 1 | 0 (off) | Make background transparent. |