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GDAL
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Warp control options for use with GDALWarpOperation::Initialize()
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#include <gdalwarper.h>
Warp control options for use with GDALWarpOperation::Initialize()
| double GDALWarpOptions::dfCutlineBlendDist |
Optional blending distance to apply across cutline in pixels, default is zero.
| double GDALWarpOptions::dfWarpMemoryLimit |
In bytes, 0.0 for internal default
| GDALResampleAlg GDALWarpOptions::eResampleAlg |
Resampling algorithm to use
| GDALDataType GDALWarpOptions::eWorkingDataType |
data type to use during warp operation, GDT_Unknown lets the algorithm select the type
| void* GDALWarpOptions::hCutline |
Optional OGRPolygonH for a masking cutline.
| GDALDatasetH GDALWarpOptions::hDstDS |
Destination image dataset - may be NULL if only using GDALWarpOperation::WarpRegionToBuffer().
| GDALDatasetH GDALWarpOptions::hSrcDS |
Source image dataset.
| int GDALWarpOptions::nBandCount |
Number of bands to process, may be 0 to select all bands.
| int GDALWarpOptions::nDstAlphaBand |
The dest. band so use as an alpha (transparency) value, 0=disabled
| int GDALWarpOptions::nSrcAlphaBand |
The source band so use as an alpha (transparency) value, 0=disabled
| double* GDALWarpOptions::padfDstNoDataImag |
The "nodata" value imaginary component - may be NULL even if real component is provided. Note that warp operations only use real component for flagging invalid data.
| double* GDALWarpOptions::padfDstNoDataReal |
The "nodata" value real component for each output band, if NULL there isn't one
| double* GDALWarpOptions::padfSrcNoDataImag |
The "nodata" value imaginary component - may be NULL even if real component is provided. This value is not used to flag invalid values. Only the real component is used.
| double* GDALWarpOptions::padfSrcNoDataReal |
The "nodata" value real component for each input band, if NULL there isn't one
| int* GDALWarpOptions::panDstBands |
The band numbers for the destination bands to process (1 based)
| int* GDALWarpOptions::panSrcBands |
The band numbers for the source bands to process (1 based)
| GDALMaskFunc* GDALWarpOptions::papfnSrcPerBandValidityMaskFunc |
Unused.
Must be NULL
| void** GDALWarpOptions::papSrcPerBandValidityMaskFuncArg |
Unused.
Must be NULL
| char ** GDALWarpOptions::papszWarpOptions |
A string list of additional options controlling the warp operation in name=value format.
A suitable string list can be prepared with CSLSetNameValue().
The following values are currently supported:
INIT_DEST=[value] or INIT_DEST=NO_DATA: This option forces the destination image to be initialized to the indicated value (for all bands) or indicates that it should be initialized to the NO_DATA value in padfDstNoDataReal/padfDstNoDataImag. If this value isn't set the destination image will be read and overlaid.
WRITE_FLUSH=YES/NO: This option forces a flush to disk of data after each chunk is processed. In some cases this helps ensure a serial writing of the output data otherwise a block of data may be written to disk each time a block of data is read for the input buffer resulting in a lot of extra seeking around the disk, and reduced IO throughput. The default at this time is NO.
SKIP_NOSOURCE=YES/NO: Skip all processing for chunks for which there is no corresponding input data. This will disable initializing the destination (INIT_DEST) and all other processing, and so should be used carefully. Mostly useful to short circuit a lot of extra work in mosaicing situations. Starting with GDAL 2.4, gdalwarp will automatically enable this option when it is assumed to be safe to do so.
UNIFIED_SRC_NODATA=YES/NO/PARTIAL: This setting determines how to take into account nodata values when there are several input bands.
Example with nodata values at (1, 2, 3) and target alpha band requested. <ul> <li>input pixel = (1, 2, 3) ==> output pixel = (0, 0, 0, 0)</li> <li>input pixel = (1, 2, 127) ==> output pixel = (1, 2, 127, 255)</li> </ul>
When NO, nodata masking values is considered independently for each band. A potential target alpha band will always be valid if there are multiple bands.
Example with nodata values at (1, 2, 3) and target alpha band requested.
Note: NO was the default behavior before GDAL 3.3.2
When PARTIAL, or not specified at all (default behavior), nodata masking values is considered independently for each band. But, and this is the difference with NO, if for a given pixel, it evaluates to the nodata value of each band, the target pixel is considered as globally invalid, which impacts the value of a potential target alpha band.
Note: PARTIAL is new to GDAL 3.3.2 and should not be used with earlier versions. The default behavior of GDAL < 3.3.2 was NO.
Example with nodata values at (1, 2, 3) and target alpha band requested.
CUTLINE: This may contain the WKT geometry for a cutline. It will be converted into a geometry by GDALWarpOperation::Initialize() and assigned to the GDALWarpOptions hCutline field. The coordinates must be expressed in source pixel/line coordinates. Note: this is different from the assumptions made for the -cutline option of the gdalwarp utility !
CUTLINE_BLEND_DIST: This may be set with a distance in pixels which will be assigned to the dfCutlineBlendDist field in the GDALWarpOptions.
CUTLINE_ALL_TOUCHED: This defaults to FALSE, but may be set to TRUE to enable ALL_TOUCHEd mode when rasterizing cutline polygons. This is useful to ensure that that all pixels overlapping the cutline polygon will be selected, not just those whose center point falls within the polygon.
XSCALE: Ratio expressing the resampling factor (number of destination pixels per source pixel) along the target horizontal axis. The scale is used to determine the number of source pixels along the x-axis that are considered by the resampling algorithm. Equals to one for no resampling, below one for downsampling and above one for upsampling. This is automatically computed, for each processing chunk, and may thus vary among them, depending on the shape of output regions vs input regions. Such variations can be undesired in some situations. If the resampling factor can be considered as constant over the warped area, setting a constant value can lead to more reproducible pixel output.
YSCALE: Same as XSCALE, but along the horizontal axis.
OPTIMIZE_SIZE: This defaults to FALSE, but may be set to TRUE typically when writing to a compressed dataset (GeoTIFF with COMPRESS creation option set for example) for achieving a smaller file size. This is achieved by writing at once data aligned on full blocks of the target dataset, which avoids partial writes of compressed blocks and lost space when they are rewritten at the end of the file. However sticking to target block size may cause major processing slowdown for some particular reprojections. Starting with GDAL 3.8, OPTIMIZE_SIZE mode is automatically enabled when it is safe to do so. As this parameter influences the shape of warping chunk, and by default the XSCALE and YSCALE parameters are computed per warping chunk, this parameter may influence the pixel output.
NUM_THREADS: (GDAL >= 1.10) Can be set to a numeric value or ALL_CPUS to set the number of threads to use to parallelize the computation part of the warping. If not set, computation will be done in a single thread.
STREAMABLE_OUTPUT: (GDAL >= 2.0) This defaults to FALSE, but may be set to TRUE typically when writing to a streamed file. The gdalwarp utility automatically sets this option when writing to /vsistdout/ or a named pipe (on Unix). This option has performance impacts for some reprojections. Note: band interleaved output is not currently supported by the warping algorithm in a streamable compatible way.
SRC_COORD_PRECISION: (GDAL >= 2.0). Advanced setting. This defaults to 0, to indicate that no rounding of computing source image coordinates corresponding to the target image must be done. If greater than 0 (and typically below 1), this value, expressed in pixel, will be used to round computed source image coordinates. The purpose of this option is to make the results of warping with the approximated transformer more reproducible and not sensitive to changes in warping memory size. To achieve that, SRC_COORD_PRECISION must be at least 10 times greater than the error threshold. The higher the SRC_COORD_PRECISION/error_threshold ratio, the higher the performance will be, since exact reprojections must statistically be done with a frequency of 4*error_threshold/SRC_COORD_PRECISION.
SRC_ALPHA_MAX: (GDAL >= 2.2). Maximum value for the alpha band of the source dataset. If the value is not set and the alpha band has a NBITS metadata item, it is used to set SRC_ALPHA_MAX = 2^NBITS-1. Otherwise, if the value is not set and the alpha band is of type UInt16 (resp Int16), 65535 (resp 32767) is used. Otherwise, 255 is used.
Normally when computing the source raster data to load to generate a particular output area, the warper samples transforms 21 points along each edge of the destination region back onto the source file, and uses this to compute a bounding window on the source image that is sufficient. Depending on the transformation in effect, the source window may be a bit too small, or even missing large areas. Problem situations are those where the transformation is very non-linear or "inside out". Examples are transforming from WGS84 to Polar Stereographic for areas around the pole, or transformations where some of the image is untransformable. The following options provide some additional control to deal with errors in computing the source window:
SAMPLE_GRID=YES/NO: Setting this option to YES will force the sampling to include internal points as well as edge points which can be important if the transformation is esoteric inside out, or if large sections of the destination image are not transformable into the source coordinate system.
SAMPLE_STEPS: Modifies the density of the sampling grid. The default number of steps is 21. Increasing this can increase the computational cost, but improves the accuracy with which the source region is computed. Starting with GDAL 3.7, this can be set to ALL to mean to sample along all edge points of the destination region (if SAMPLE_GRID=NO or not specified), or all points of the destination region if SAMPLE_GRID=YES.
MULT_FACTOR_VERTICAL_SHIFT: Multiplication factor for the vertical shift. Default 1.0
EXCLUDED_VALUES: (GDAL >= 3.9) Comma-separated tuple of values (thus typically "R,G,B"), that are ignored as contributing source pixels during resampling. The number of values in the tuple must be the same as the number of bands, excluding the alpha band. Several tuples of excluded values may be specified using the "(R1,G1,B2),(R2,G2,B2)" syntax. Only taken into account by Average currently. This concept is a bit similar to nodata/alpha, but the main difference is that pixels matching one of the excluded value tuples are still considered as valid, when determining the target pixel validity/density.
EXCLUDED_VALUES_PCT_THRESHOLD=[0-100]: (GDAL >= 3.9) Minimum percentage of source pixels that must be set at one of the EXCLUDED_VALUES to cause the excluded value, that is in majority among source pixels, to be used as the target pixel value. Default value is 50 (%). Only taken into account by Average currently.
NODATA_VALUES_PCT_THRESHOLD=[0-100]: (GDAL >= 3.9) Minimum percentage of source pixels that must be at nodata (or alpha=0 or any other way to express transparent pixel) to cause the target pixel value to not be set. Default value is 100 (%), which means that a target pixel is not set only if all contributing source pixels are not set. Note that NODATA_VALUES_PCT_THRESHOLD is taken into account before EXCLUDED_VALUES_PCT_THRESHOLD. Only taken into account by Average currently.
| void* GDALWarpOptions::pDstDensityMaskFuncArg |
Unused.
Must be NULL
| void* GDALWarpOptions::pDstValidityMaskFuncArg |
Unused.
Must be NULL
| GDALMaskFunc GDALWarpOptions::pfnDstDensityMaskFunc |
Unused.
Must be NULL
| GDALMaskFunc GDALWarpOptions::pfnDstValidityMaskFunc |
Unused.
Must be NULL
| CPLErr(* GDALWarpOptions::pfnPostWarpChunkProcessor) (void *pKern, void *pArg) |
Unused.
Must be NULL
| CPLErr(* GDALWarpOptions::pfnPreWarpChunkProcessor) (void *pKern, void *pArg) |
Unused.
Must be NULL
| GDALProgressFunc GDALWarpOptions::pfnProgress |
GDALProgressFunc() compatible progress reporting function, or NULL if there isn't one.
| GDALMaskFunc GDALWarpOptions::pfnSrcDensityMaskFunc |
Unused.
Must be NULL
| GDALMaskFunc GDALWarpOptions::pfnSrcValidityMaskFunc |
Unused.
Must be NULL
| GDALTransformerFunc GDALWarpOptions::pfnTransformer |
Type of spatial point transformer function
| void* GDALWarpOptions::pPostWarpProcessorArg |
Unused.
Must be NULL
| void* GDALWarpOptions::pPreWarpProcessorArg |
Unused.
Must be NULL
| void* GDALWarpOptions::pProgressArg |
Callback argument to be passed to pfnProgress.
| void* GDALWarpOptions::pSrcDensityMaskFuncArg |
Unused.
Must be NULL
| void* GDALWarpOptions::pSrcValidityMaskFuncArg |
Unused.
Must be NULL
| void* GDALWarpOptions::pTransformerArg |
Handle to image transformer setup structure
1.9.8