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# gdal_alg.h File Reference

`#include "gdal.h"`
`#include "cpl_minixml.h"`
`#include "ogr_api.h"`

Go to the source code of this file.

## Classes
struct | GDALTransformerInfo
struct | OGRContourWriterInfo
## Typedefs
typedef int(*) | GDALTransformerFunc (void *pTransformerArg, int bDstToSrc, int nPointCount, double *x, double *y, double *z, int *panSuccess)
typedef CPLErr(*) | GDALContourWriter (double dfLevel, int nPoints, double *padfX, double *padfY, void *)
typedef void * | GDALContourGeneratorH
typedef void(*) | llScanlineFunc (void *pCBData, int nY, int nXStart, int nXEnd)
## Functions
int | GDALComputeMedianCutPCT (GDALRasterBandH hRed, GDALRasterBandH hGreen, GDALRasterBandH hBlue, int(*pfnIncludePixel)(int, int, void *), int nColors, GDALColorTableH hColorTable, GDALProgressFunc pfnProgress, void *pProgressArg)
int | GDALDitherRGB2PCT (GDALRasterBandH hRed, GDALRasterBandH hGreen, GDALRasterBandH hBlue, GDALRasterBandH hTarget, GDALColorTableH hColorTable, GDALProgressFunc pfnProgress, void *pProgressArg)
int | GDALChecksumImage (GDALRasterBandH hBand, int nXOff, int nYOff, int nXSize, int nYSize)
void | GDALDestroyTransformer (void *pTransformerArg)
void * | GDALCreateGenImgProjTransformer (GDALDatasetH hSrcDS, const char *pszSrcWKT, GDALDatasetH hDstDS, const char *pszDstWKT, int bGCPUseOK, double dfGCPErrorThreshold, int nOrder)
void | GDALSetGenImgProjTransformerDstGeoTransform (void *, const double *)
void | GDALDestroyGenImgProjTransformer (void *)
int | GDALGenImgProjTransform (void *pTransformArg, int bDstToSrc, int nPointCount, double *x, double *y, double *z, int *panSuccess)
void * | GDALCreateReprojectionTransformer (const char *pszSrcWKT, const char *pszDstWKT)
void | GDALDestroyReprojectionTransformer (void *)
int | GDALReprojectionTransform (void *pTransformArg, int bDstToSrc, int nPointCount, double *x, double *y, double *z, int *panSuccess)
void * | GDALCreateGCPTransformer (int nGCPCount, const GDAL_GCP *pasGCPList, int nReqOrder, int bReversed)
void | GDALDestroyGCPTransformer (void *pTransformArg)
int | GDALGCPTransform (void *pTransformArg, int bDstToSrc, int nPointCount, double *x, double *y, double *z, int *panSuccess)
void * | GDALCreateTPSTransformer (int nGCPCount, const GDAL_GCP *pasGCPList, int bReversed)
void | GDALDestroyTPSTransformer (void *pTransformArg)
int | GDALTPSTransform (void *pTransformArg, int bDstToSrc, int nPointCount, double *x, double *y, double *z, int *panSuccess)
void * | GDALCreateRPCTransformer (GDALRPCInfo *psRPC, int bReversed, double dfPixErrThreshold)
void | GDALDestroyRPCTransformer (void *pTransformArg)
int | GDALRPCTransform (void *pTransformArg, int bDstToSrc, int nPointCount, double *x, double *y, double *z, int *panSuccess)
void * | GDALCreateGeoLocTransformer (GDALDatasetH hBaseDS, char **papszGeolocationInfo, int bReversed)
void | GDALDestroyGeoLocTransformer (void *pTransformArg)
int | GDALGeoLocTransform (void *pTransformArg, int bDstToSrc, int nPointCount, double *x, double *y, double *z, int *panSuccess)
void * | GDALCreateApproxTransformer (GDALTransformerFunc pfnRawTransformer, void *pRawTransformerArg, double dfMaxError)
void | GDALApproxTransformerOwnsSubtransformer (void *pCBData, int bOwnFlag)
void | GDALDestroyApproxTransformer (void *pApproxArg)
int | GDALApproxTransform (void *pTransformArg, int bDstToSrc, int nPointCount, double *x, double *y, double *z, int *panSuccess)
int | GDALSimpleImageWarp (GDALDatasetH hSrcDS, GDALDatasetH hDstDS, int nBandCount, int *panBandList, GDALTransformerFunc pfnTransform, void *pTransformArg, GDALProgressFunc pfnProgress, void *pProgressArg, char **papszWarpOptions)
CPLErr | GDALSuggestedWarpOutput (GDALDatasetH hSrcDS, GDALTransformerFunc pfnTransformer, void *pTransformArg, double *padfGeoTransformOut, int *pnPixels, int *pnLines)
CPLErr | GDALSuggestedWarpOutput2 (GDALDatasetH hSrcDS, GDALTransformerFunc pfnTransformer, void *pTransformArg, double *padfGeoTransformOut, int *pnPixels, int *pnLines, double *padfExtents, int nOptions)
CPLXMLNode * | GDALSerializeTransformer (GDALTransformerFunc pfnFunc, void *pTransformArg)
CPLErr | GDALDeserializeTransformer (CPLXMLNode *psTree, GDALTransformerFunc *ppfnFunc, void **ppTransformArg)
GDALContourGeneratorH | GDAL_CG_Create (int nWidth, int nHeight, int bNoDataSet, double dfNoDataValue, double dfContourInterval, double dfContourBase, GDALContourWriter pfnWriter, void *pCBData)
CPLErr | GDAL_CG_FeedLine (GDALContourGeneratorH hCG, double *padfScanline)
void | GDAL_CG_Destroy (GDALContourGeneratorH hCG)
CPLErr | OGRContourWriter (double, int, double *, double *, void *pInfo)
CPLErr | GDALContourGenerate (GDALRasterBandH hBand, double dfContourInterval, double dfContourBase, int nFixedLevelCount, double *padfFixedLevels, int bUseNoData, double dfNoDataValue, void *hLayer, int iIDField, int iElevField, GDALProgressFunc pfnProgress, void *pProgressArg)
void | GDALdllImageFilledPolygon (int nRasterXSize, int nRasterYSize, int nPartCount, int *panPartSize, double *padfX, double *padfY, llScanlineFunc pfnScanlineFunc, void *pCBData)
CPLErr | GDALRasterizeGeometries (GDALDatasetH hDS, int nBandCount, int *panBandList, int nGeomCount, OGRGeometryH *pahGeometries, GDALTransformerFunc pfnTransformer, void *pTransformArg, double *padfGeomBurnValue, char **papszOptions, GDALProgressFunc pfnProgress, void *pProgressArg)

## Detailed Description

Public (C callable) GDAL algorithm entry points, and definitions.

## Typedef Documentation

int GDALTransformerFunc

Generic signature for spatial point transformers.

This function signature is used for a variety of functions that accept passed in functions used to transform point locations between two coordinate spaces.

The GDALCreateGenImgProjTransformer(), GDALCreateReprojectionTransformer(), GDALCreateGCPTransformer() and GDALCreateApproxTransformer() functions can be used to prepare argument data for some built-in transformers. As well, applications can implement their own transformers to the following signature.

    typedef int
    (*GDALTransformerFunc)( void *pTransformerArg,
                            int bDstToSrc, int nPointCount,
                            double *x, double *y, double *z, int *panSuccess );

Parameters:

  | pTransformerArg | application supplied callback data used by the transformer.
  | bDstToSrc | if TRUE the transformation will be from the destination coordinate space to the source coordinate system, otherwise the transformation will be from the source coordinate system to the destination coordinate system.
  | nPointCount | number of points in the x, y and z arrays.
  | x | input X coordinates. Results returned in same array.
  | y | input Y coordinates. Results returned in same array.
  | z | input Z coordinates. Results returned in same array.
  | panSuccess | array of ints in which success (TRUE) or failure (FALSE) flags are returned for the translation of each point.

Returns:
  TRUE if the overall transformation succeeds (though some individual points may have failed) or FALSE if the overall transformation fails.

## Function Documentation

int GDALApproxTransform | ( | void * | pCBData,
|  | int | bDstToSrc,
|  | int | nPoints,
|  | double * | x,
|  | double * | y,
|  | double * | z,
|  | int * | panSuccess |
| ) |  |  |

Perform approximate transformation.

Actually performs the approximate transformation described in GDALCreateApproxTransformer(). This function matches the GDALTransformerFunc() signature. Details of the arguments are described there.

int GDALChecksumImage | ( | GDALRasterBandH | hBand,
|  | int | nXOff,
|  | int | nYOff,
|  | int | nXSize,
|  | int | nYSize |
| ) |  |  |

Compute checksum for image region.

Computes a 16bit (0-65535) checksum from a region of raster data on a GDAL supported band. Floating point data is converted to 32bit integer so decimal portions of such raster data will not affect the checksum. Real and Imaginary components of complex bands influence the result.

Parameters:

  | hBand | the raster band to read from.
  | nXOff | pixel offset of window to read.
  | nYOff | line offset of window to read.
  | nXSize | pixel size of window to read.
  | nYSize | line size of window to read.

Returns:
  Checksum value.

int GDALComputeMedianCutPCT | ( | GDALRasterBandH | hRed,
|  | GDALRasterBandH | hGreen,
|  | GDALRasterBandH | hBlue,
|  | int(*)(int, int, void *) | pfnIncludePixel,
|  | int | nColors,
|  | GDALColorTableH | hColorTable,
|  | GDALProgressFunc | pfnProgress,
|  | void * | pProgressArg |
| ) |  |  |

Compute optimal PCT for RGB image.

This function implements a median cut algorithm to compute an "optimal" pseudocolor table for representing an input RGB image. This PCT could then be used with GDALDitherRGB2PCT() to convert a 24bit RGB image into an eightbit pseudo-colored image.

This code was based on the tiffmedian.c code from libtiff (www.libtiff.org) which was based on a paper by Paul Heckbert:

     *   "Color  Image Quantization for Frame Buffer Display", Paul
     *   Heckbert, SIGGRAPH proceedings, 1982, pp. 297-307.
     *

The red, green and blue input bands do not necessarily need to come from the same file, but they must be the same width and height. They will be clipped to 8bit during reading, so non-eight bit bands are generally inappropriate.

Parameters:

  | hRed | Red input band.
  | hGreen | Green input band.
  | hBlue | Blue input band.
  | pfnIncludePixel | function used to test which pixels should be included in the analysis. At this time this argument is ignored and all pixels are utilized. This should normally be NULL.
  | nColors | the desired number of colors to be returned (2-256).
  | hColorTable | the colors will be returned in this color table object.
  | pfnProgress | callback for reporting algorithm progress matching the GDALProgressFunc() semantics. May be NULL.
  | pProgressArg | callback argument passed to pfnProgress.

Returns:
  returns CE_None on success or CE_Failure if an error occurs.

CPLErr GDALContourGenerate | ( | GDALRasterBandH | hBand,
|  | double | dfContourInterval,
|  | double | dfContourBase,
|  | int | nFixedLevelCount,
|  | double * | padfFixedLevels,
|  | int | bUseNoData,
|  | double | dfNoDataValue,
|  | void * | hLayer,
|  | int | iIDField,
|  | int | iElevField,
|  | GDALProgressFunc | pfnProgress,
|  | void * | pProgressArg |
| ) |  |  |

Create vector contours from raster DEM.

This algorithm will generate contours vectors for the input raster band on the requested set of contour levels. The vector contours are written to the passed in OGR vector layer. Also, a NODATA value may be specified to identify pixels that should not be considered in contour line generation.

The gdal/apps/gdal_contour.cpp mainline can be used as an example of how to use this function.

ALGORITHM RULES

For contouring purposes raster pixel values are assumed to represent a point value at the center of the corresponding pixel region. For the purpose of contour generation we virtually connect each pixel center to the values to the left, right, top and bottom. We assume that the pixel value is linearly interpolated between the pixel centers along each line, and determine where (if any) contour lines will appear onlong these line segements. Then the contour crossings are connected.

This means that contour lines nodes won't actually be on pixel edges, but rather along vertical and horizontal lines connecting the pixel centers.

    General Case:

          5 |                  | 3
         -- + ---------------- + --
            |                  |
            |                  |
            |                  |
            |                  |
         10 +                  |
            |\                 |
            | \                |
         -- + -+-------------- + --
         12 |  10              | 1

    Saddle Point:

          5 |                  | 12
         -- + -------------+-- + --
            |               \  |
            |                 \|
            |                  +
            |                  |
            +                  |
            |\                 |
            | \                |
         -- + -+-------------- + --
         12 |                  | 1

    or:

          5 |                  | 12
         -- + -------------+-- + --
            |          __/     |
            |      ___/        |
            |  ___/          __+
            | /           __/  |
            +'         __/     |
            |       __/        |
            |   ,__/           |
         -- + -+-------------- + --
         12 |                  | 1

Nodata:

In the "nodata" case we treat the whole nodata pixel as a no-mans land. We extend the corner pixels near the nodata out to half way and then construct extra lines from those points to the center which is assigned an averaged value from the two nearby points (in this case (12+3+5)/3).

          5 |                  | 3
         -- + ---------------- + --
            |                  |
            |                  |
            |      6.7         |
            |        +---------+ 3
         10 +___     |
            |   \____+ 10
            |        |
         -- + -------+        +
         12 |       12           (nodata)

Parameters:

  | hBand | The band to read raster data from. The whole band will be processed.
  | dfContourInterval | The elevation interval between contours generated.
  | dfContourBase | The "base" relative to which contour intervals are applied. This is normally zero, but could be different. To generate 10m contours at 5, 15, 25, ... the ContourBase would be 5.
  | nFixedLevelCount | The number of fixed levels. If this is greater than zero, then fixed levels will be used, and ContourInterval and ContourBase are ignored.
  | padfFixedLevels | The list of fixed contour levels at which contours should be generated. It will contain FixedLevelCount entries, and may be NULL if fixed levels are disabled (FixedLevelCount = 0).
  | bUseNoData | If TRUE the dfNoDataValue will be used.
  | dfNoDataValue | the value to use as a "nodata" value. That is, a pixel value which should be ignored in generating contours as if the value of the pixel were not known.
  | hLayer | the layer to which new contour vectors will be written. Each contour will have a LINESTRING geometry attached to it. This is really of type OGRLayerH, but void * is used to avoid pulling the ogr_api.h file in here.
  | iIDField | if not -1 this will be used as a field index to indicate where a unique id should be written for each feature (contour) written.
  | iElevField | if not -1 this will be used as a field index to indicate where the elevation value of the contour should be written.
  | pfnProgress | a GDALProgressFunc that may be used to report progress to the user, or to interrupt the algorithm. May be NULL if not required.
  | pProgressArg | the callback data for the pfnProgress function.

Returns:
  CE_None on success or CE_Failure if an error occurs.

void* GDALCreateApproxTransformer | ( | GDALTransformerFunc | pfnBaseTransformer,
|  | void * | pBaseTransformArg,
|  | double | dfMaxError |
| ) |  |  |

Create an approximating transformer.

This function creates a context for an approximated transformer. Basically a high precision transformer is supplied as input and internally linear approximations are computed to generate results to within a defined precision.

The approximation is actually done at the point where GDALApproxTransform() calls are made, and depend on the assumption that the roughly linear. The first and last point passed in must be the extreme values and the intermediate values should describe a curve between the end points. The approximator transforms and center using the approximate transformer, and then compares the true middle transformed value to a linear approximation based on the end points. If the error is within the supplied threshold then the end points are used to linearly approximate all the values otherwise the inputs points are split into two smaller sets, and the function recursively called till a sufficiently small set of points if found that the linear approximation is OK, or that all the points are exactly computed.

This function is very suitable for approximating transformation results from output pixel/line space to input coordinates for warpers that operate on one input scanline at a time. Care should be taken using it in other circumstances as little internal validation is done, in order to keep things fast.

Parameters:

  | pfnBaseTransformer | the high precision transformer which should be approximated.
  | pBaseTransformArg | the callback argument for the high precision transformer.
  | dfMaxError | the maximum cartesian error in the "output" space that is to be accepted in the linear approximation.

Returns:
  callback pointer suitable for use with GDALApproxTransform(). It should be deallocated with GDALDestroyApproxTransformer().

void* GDALCreateGCPTransformer | ( | int | nGCPCount,
|  | const GDAL_GCP * | pasGCPList,
|  | int | nReqOrder,
|  | int | bReversed |
| ) |  |  |

Create GCP based polynomial transformer.

Computes least squares fit polynomials from a provided set of GCPs, and stores the coefficients for later transformation of points between pixel/line and georeferenced coordinates.

The return value should be used as a TransformArg in combination with the transformation function GDALGCPTransform which fits the GDALTransformerFunc signature. The returned transform argument should be deallocated with GDALDestroyGCPTransformer when no longer needed.

This function may fail (returning NULL) if the provided set of GCPs are inadequate for the requested order, the determinate is zero or they are otherwise "ill conditioned".

Note that 2nd order requires at least 6 GCPs, and 3rd order requires at least 10 gcps. If nReqOrder is 0 the highest order possible with the provided gcp count will be used.

Parameters:

  | nGCPCount | the number of GCPs in pasGCPList.
  | pasGCPList | an array of GCPs to be used as input.
  | nReqOrder | the requested polynomial order. It should be 1, 2 or 3.

Returns:
  the transform argument or NULL if creation fails.

void* GDALCreateGenImgProjTransformer | ( | GDALDatasetH | hSrcDS,
|  | const char * | pszSrcWKT,
|  | GDALDatasetH | hDstDS,
|  | const char * | pszDstWKT,
|  | int | bGCPUseOK,
|  | double | dfGCPErrorThreshold,
|  | int | nOrder |
| ) |  |  |

Create image to image transformer.

This function creates a transformation object that maps from pixel/line coordinates on one image to pixel/line coordinates on another image. The images may potentially be georeferenced in different coordinate systems, and may used GCPs to map between their pixel/line coordinates and georeferenced coordinates (as opposed to the default assumption that their geotransform should be used).

This transformer potentially performs three concatenated transformations.

The first stage is from source image pixel/line coordinates to source image georeferenced coordinates, and may be done using the geotransform, or if not defined using a polynomial model derived from GCPs. If GCPs are used this stage is accomplished using GDALGCPTransform().

The second stage is to change projections from the source coordinate system to the destination coordinate system, assuming they differ. This is accomplished internally using GDALReprojectionTransform().

The third stage is converting from destination image georeferenced coordinates to destination image coordinates. This is done using the destination image geotransform, or if not available, using a polynomial model derived from GCPs. If GCPs are used this stage is accomplished using GDALGCPTransform(). This stage is skipped if hDstDS is NULL when the transformation is created.

Parameters:

  | hSrcDS | source dataset, or NULL.
  | pszSrcWKT | the coordinate system for the source dataset. If NULL, it will be read from the dataset itself.
  | hDstDS | destination dataset (or NULL).
  | pszDstWKT | the coordinate system for the destination dataset. If NULL, and hDstDS not NULL, it will be read from the destination dataset.
  | bGCPUseOK | TRUE if GCPs should be used if the geotransform is not available on the source dataset (not destination).
  | dfGCPErrorThreshold | the maximum error allowed for the GCP model to be considered valid. Exact semantics not yet defined.
  | nOrder | the maximum order to use for GCP derived polynomials if possible. Use 0 to autoselect, or -1 for thin plate splines.

Returns:
  handle suitable for use GDALGenImgProjTransform(), and to be deallocated with GDALDestroyGenImgProjTransformer().

void* GDALCreateReprojectionTransformer | ( | const char * | pszSrcWKT,
|  | const char * | pszDstWKT |
| ) |  |  |

Create reprojection transformer.

Creates a callback data structure suitable for use with GDALReprojectionTransformation() to represent a transformation from one geographic or projected coordinate system to another. On input the coordinate systems are described in OpenGIS WKT format.

Internally the OGRCoordinateTransformation object is used to implement the reprojection.

Parameters:

  | pszSrcWKT | the coordinate system for the source coordinate system.
  | pszDstWKT | the coordinate system for the destination coordinate system.

Returns:
  Handle for use with GDALReprojectionTransform(), or NULL if the system fails to initialize the reprojection.

void* GDALCreateTPSTransformer | ( | int | nGCPCount,
|  | const GDAL_GCP * | pasGCPList,
|  | int | bReversed |
| ) |  |  |

Create Thin Plate Spline transformer from GCPs.

The thin plate spline transformer produces exact transformation at all control points and smoothly varying transformations between control points with greatest influence from local control points. It is suitable for for many applications not well modelled by polynomial transformations.

Creating the TPS transformer involves solving systems of linear equations related to the number of control points involved. This solution is computed within this function call. It can be quite an expensive operation for large numbers of GCPs. For instance, for reference, it takes on the order of 10s for 400 GCPs on a 2GHz Athlon processor.

TPS Transformers are serializable.

The GDAL Thin Plate Spline transformer is based on code provided by Gilad Ronnen on behalf of VIZRT Inc (http://www.visrt.com). Incorporation of the algorithm into GDAL was supported by the Centro di Ecologia Alpina (http://www.cealp.it).

Parameters:

  | nGCPCount | the number of GCPs in pasGCPList.
  | pasGCPList | an array of GCPs to be used as input.
  | bReversed |

Returns:
  the transform argument or NULL if creation fails.

void GDALDestroyApproxTransformer | ( | void * | pCBData | ) |

Cleanup approximate transformer.

Deallocates the resources allocated by GDALCreateApproxTransformer().

Parameters:

  | pCBData | callback data originally returned by GDALCreateApproxTransformer().

void GDALDestroyGCPTransformer | ( | void * | pTransformArg | ) |

Destroy GCP transformer.

This function is used to destroy information about a GCP based polynomial transformation created with GDALCreateGCPTransformer().

Parameters:

  | pTransformArg | the transform arg previously returned by GDALCreateGCPTransformer().

void GDALDestroyGenImgProjTransformer | ( | void * | hTransformArg | ) |

GenImgProjTransformer deallocator.

This function is used to deallocate the handle created with GDALCreateGenImgProjTransformer().

Parameters:

  | hTransformArg | the handle to deallocate.

void GDALDestroyReprojectionTransformer | ( | void * | pTransformAlg | ) |

Destroy reprojection transformation.

Parameters:

  | pTransformArg | the transformation handle returned by GDALCreateReprojectionTransformer().

void GDALDestroyTPSTransformer | ( | void * | pTransformArg | ) |

Destroy TPS transformer.

This function is used to destroy information about a GCP based polynomial transformation created with GDALCreateTPSTransformer().

Parameters:

  | pTransformArg | the transform arg previously returned by GDALCreateTPSTransformer().

int GDALDitherRGB2PCT | ( | GDALRasterBandH | hRed,
|  | GDALRasterBandH | hGreen,
|  | GDALRasterBandH | hBlue,
|  | GDALRasterBandH | hTarget,
|  | GDALColorTableH | hColorTable,
|  | GDALProgressFunc | pfnProgress,
|  | void * | pProgressArg |
| ) |  |  |

24bit to 8bit conversion with dithering.

This functions utilizes Floyd-Steinberg dithering in the process of converting a 24bit RGB image into a pseudocolored 8bit image using a provided color table.

The red, green and blue input bands do not necessarily need to come from the same file, but they must be the same width and height. They will be clipped to 8bit during reading, so non-eight bit bands are generally inappropriate. Likewise the hTarget band will be written with 8bit values and must match the width and height of the source bands.

Parameters:

  | hRed | Red input band.
  | hGreen | Green input band.
  | hBlue | Blue input band.
  | hTarget | Output band.
  | hColorTable | the color table to use with the output band.
  | pfnProgress | callback for reporting algorithm progress matching the GDALProgressFunc() semantics. May be NULL.
  | pProgressArg | callback argument passed to pfnProgress.

Returns:
  CE_None on success or CE_Failure if an error occurs.

int GDALGCPTransform | ( | void * | pTransformArg,
|  | int | bDstToSrc,
|  | int | nPointCount,
|  | double * | x,
|  | double * | y,
|  | double * | z,
|  | int * | panSuccess |
| ) |  |  |

Transforms point based on GCP derived polynomial model.

This function matches the GDALTransformerFunc signature, and can be used to transform one or more points from pixel/line coordinates to georeferenced coordinates (SrcToDst) or vice versa (DstToSrc).

Parameters:

  | pTransformArg | return value from GDALCreateGCPTransformer().
  | bDstToSrc | TRUE if transformation is from the destination (georeferenced) coordinates to pixel/line or FALSE when transforming from pixel/line to georeferenced coordinates.
  | nPointCount | the number of values in the x, y and z arrays.
  | x | array containing the X values to be transformed.
  | y | array containing the Y values to be transformed.
  | z | array containing the Z values to be transformed.
  | panSuccess | array in which a flag indicating success (TRUE) or failure (FALSE) of the transformation are placed.

Returns:
  TRUE.

int GDALGenImgProjTransform | ( | void * | pTransformArg,
|  | int | bDstToSrc,
|  | int | nPointCount,
|  | double * | padfX,
|  | double * | padfY,
|  | double * | padfZ,
|  | int * | panSuccess |
| ) |  |  |

Perform general image reprojection transformation.

Actually performs the transformation setup in GDALCreateGenImgProjTransformer(). This function matches the signature required by the GDALTransformerFunc(), and more details on the arguments can be found in that topic.

CPLErr GDALRasterizeGeometries | ( | GDALDatasetH | hDS,
|  | int | nBandCount,
|  | int * | panBandList,
|  | int | nGeomCount,
|  | OGRGeometryH * | pahGeometries,
|  | GDALTransformerFunc | pfnTransformer,
|  | void * | pTransformArg,
|  | double * | padfGeomBurnValue,
|  | char ** | papszOptions,
|  | GDALProgressFunc | pfnProgress,
|  | void * | pProgressArg |
| ) |  |  |

Burn geometries into raster.

Rasterize a list of geometric objects into a raster dataset. The geometries are passed as an array of OGRGeometry objects.

If the geometries are in the georferenced coordinates of the raster dataset, then the pfnTransform may be passed in NULL and one will be derived internally from the geotransform of the dataset. The transform needs to transform the geometry locations into pixel/line coordinates on the raster dataset.

The output raster may be of any GDAL supported datatype, though currently internally the burning is done either as GDT_Byte or GDT_Float32. This may be improved in the future. An explicit list of burn values for each geometry for each band must be passed in.

Currently only polygon, multipolygon and geometrycollections of polygons or multipolygons are supported. In the future support for points and lines may be added.

Parameters:

  | hDS | output data, must be opened in update mode.
  | nBandCount | the number of bands to be updated.
  | panBandList | the list of bands to be updated.
  | nGeomCount | the number of geometries being passed in pahGeometries.
  | pahGeometries | the array of geometries to burn in.
  | pfnTransformer | transformation to apply to geometries to put into pixel/line coordinates on raster. If NULL a geotransform based one will be created internally.
  | pTransformerArg | callback data for transformer.
  | padfGeomBurnValue | the array of values to burn into the raster. There should nBandCount values for each geometry.
  | papszOption | special options controlling rasterization, currently none are defined.
  | pfnProgress | the progress function to report completion.
  | pProgressArg | callback data for progress function.

Returns:
  CE_None on success or CE_Failure on error.

int GDALReprojectionTransform | ( | void * | pTransformArg,
|  | int | bDstToSrc,
|  | int | nPointCount,
|  | double * | padfX,
|  | double * | padfY,
|  | double * | padfZ,
|  | int * | panSuccess |
| ) |  |  |

Perform reprojection transformation.

Actually performs the reprojection transformation described in GDALCreateReprojectionTransformer(). This function matches the GDALTransformerFunc() signature. Details of the arguments are described there.

void GDALSetGenImgProjTransformerDstGeoTransform | ( | void * | hTransformArg,
|  | const double * | padfGeoTransform |
| ) |  |  |

Set GenImgProj output geotransform.

Normally the "destination geotransform", or transformation between georeferenced output coordinates and pixel/line coordinates on the destination file is extracted from the destination file by GDALCreateGenImgProjTransformer() and stored in the GenImgProj private info. However, sometimes it is inconvenient to have an output file handle with appropriate geotransform information when creating the transformation. For these cases, this function can be used to apply the destination geotransform.

Parameters:

  | hTransformArg | the handle to update.
  | padfGeoTransform | the destination geotransform to apply (six doubles).

int GDALSimpleImageWarp | ( | GDALDatasetH | hSrcDS,
|  | GDALDatasetH | hDstDS,
|  | int | nBandCount,
|  | int * | panBandList,
|  | GDALTransformerFunc | pfnTransform,
|  | void * | pTransformArg,
|  | GDALProgressFunc | pfnProgress,
|  | void * | pProgressArg,
|  | char ** | papszWarpOptions |
| ) |  |  |

Perform simple image warp.

Copies an image from a source dataset to a destination dataset applying an application defined transformation. This algorithm is called simple because it lacks many options such as resampling kernels (other than nearest neighbour), support for data types other than 8bit, and the ability to warp images without holding the entire source and destination image in memory.

The following option(s) may be passed in papszWarpOptions.

- "INIT=v[,v...]": This option indicates that the output dataset should be initialized to the indicated value in any area valid data is not written. Distinct values may be listed for each band separated by columns.

Parameters:

  | hSrcDS | the source image dataset.
  | hDstDS | the destination image dataset.
  | nBandCount | the number of bands to be warped. If zero, all bands will be processed.
  | panBandList | the list of bands to translate.
  | pfnTransform | the transformation function to call. See GDALTransformerFunc().
  | pTransformArg | the callback handle to pass to pfnTransform.
  | pfnProgress | the function used to report progress. See GDALProgressFunc().
  | pProgressArg | the callback handle to pass to pfnProgress.
  | papszWarpOptions | additional options controlling the warp.

Returns:
  TRUE if the operation completes, or FALSE if an error occurs.

CPLErr GDALSuggestedWarpOutput | ( | GDALDatasetH | hSrcDS,
|  | GDALTransformerFunc | pfnTransformer,
|  | void * | pTransformArg,
|  | double * | padfGeoTransformOut,
|  | int * | pnPixels,
|  | int * | pnLines |
| ) |  |  |

Suggest output file size.

This function is used to suggest the size, and georeferenced extents appropriate given the indicated transformation and input file. It walks the edges of the input file (approximately 20 sample points along each edge) transforming into output coordinates in order to get an extents box.

Then a resolution is computed with the intent that the length of the distance from the top left corner of the output imagery to the bottom right corner would represent the same number of pixels as in the source image. Note that if the image is somewhat rotated the diagonal taken isnt of the whole output bounding rectangle, but instead of the locations where the top/left and bottom/right corners transform. The output pixel size is always square. This is intended to approximately preserve the resolution of the input data in the output file.

The values returned in padfGeoTransformOut, pnPixels and pnLines are the suggested number of pixels and lines for the output file, and the geotransform relating those pixels to the output georeferenced coordinates.

The trickiest part of using the function is ensuring that the transformer created is from source file pixel/line coordinates to output file georeferenced coordinates. This can be accomplished with GDALCreateGenImProjTransformer() by passing a NULL for the hDstDS.

Parameters:

  | hSrcDS | the input image (it is assumed the whole input images is being transformed).
  | pfnTransformer | the transformer function.
  | pTransformArg | the callback data for the transformer function.
  | padfGeoTransformOut | the array of six doubles in which the suggested geotransform is returned.
  | pnPixels | int in which the suggest pixel width of output is returned.
  | pnLines | int in which the suggest pixel height of output is returned.

Returns:
  CE_None if successful or CE_Failure otherwise.

CPLErr GDALSuggestedWarpOutput2 | ( | GDALDatasetH | hSrcDS,
|  | GDALTransformerFunc | pfnTransformer,
|  | void * | pTransformArg,
|  | double * | padfGeoTransformOut,
|  | int * | pnPixels,
|  | int * | pnLines,
|  | double * | padfExtent,
|  | int | nOptions |
| ) |  |  |

Suggest output file size.

This function is used to suggest the size, and georeferenced extents appropriate given the indicated transformation and input file. It walks the edges of the input file (approximately 20 sample points along each edge) transforming into output coordinates in order to get an extents box.

Then a resolution is computed with the intent that the length of the distance from the top left corner of the output imagery to the bottom right corner would represent the same number of pixels as in the source image. Note that if the image is somewhat rotated the diagonal taken isnt of the whole output bounding rectangle, but instead of the locations where the top/left and bottom/right corners transform. The output pixel size is always square. This is intended to approximately preserve the resolution of the input data in the output file.

The values returned in padfGeoTransformOut, pnPixels and pnLines are the suggested number of pixels and lines for the output file, and the geotransform relating those pixels to the output georeferenced coordinates.

The trickiest part of using the function is ensuring that the transformer created is from source file pixel/line coordinates to output file georeferenced coordinates. This can be accomplished with GDALCreateGenImProjTransformer() by passing a NULL for the hDstDS.

Parameters:

  | hSrcDS | the input image (it is assumed the whole input images is being transformed).
  | pfnTransformer | the transformer function.
  | pTransformArg | the callback data for the transformer function.
  | padfGeoTransformOut | the array of six doubles in which the suggested geotransform is returned.
  | pnPixels | int in which the suggest pixel width of output is returned.
  | pnLines | int in which the suggest pixel height of output is returned.
  | padfExtent | Four entry array to return extents as (xmin, ymin, xmax, ymax).
  | nOptions | Options, currently always zero.

Returns:
  CE_None if successful or CE_Failure otherwise.

int GDALTPSTransform | ( | void * | pTransformArg,
|  | int | bDstToSrc,
|  | int | nPointCount,
|  | double * | x,
|  | double * | y,
|  | double * | z,
|  | int * | panSuccess |
| ) |  |  |

Transforms point based on GCP derived polynomial model.

This function matches the GDALTransformerFunc signature, and can be used to transform one or more points from pixel/line coordinates to georeferenced coordinates (SrcToDst) or vice versa (DstToSrc).

Parameters:

  | pTransformArg | return value from GDALCreateTPSTransformer().
  | bDstToSrc | TRUE if transformation is from the destination (georeferenced) coordinates to pixel/line or FALSE when transforming from pixel/line to georeferenced coordinates.
  | nPointCount | the number of values in the x, y and z arrays.
  | x | array containing the X values to be transformed.
  | y | array containing the Y values to be transformed.
  | z | array containing the Z values to be transformed.
  | panSuccess | array in which a flag indicating success (TRUE) or failure (FALSE) of the transformation are placed.

Returns:
  TRUE.

Generated for GDAL by 1.5.1.