L_ImgKrnManualPerspectiveCorrection

#include "ltimgkrn.h"

L_LTIMGKRN_API L_INT L_ImgKrnManualPerspectiveCorrection(srcBitmap, data, destBitmap, structSize)

BITMAPHANDLE *srcBitmap; source bitmap handle
const L_ImgKrnPerspectiveCorrectionData *data; list of points to be transformed
BITMAPHANDLE *destBitmap; destination bitmap handle
L_UINT structSize; size of the destination bitmap

Corrects the view perspective of the image.

Parameter Description
srcBitmap Pointer to the source bitmap handle referencing the bitmap to be transformed.
data Pointer to L_ImgKrnPerspectiveCorrectionData structure that contains a list of points that will be transformed to match the location of the mapped points list.
destBitmap Pointer to the handle of the transformed destination bitmap.
structSize Size, in bytes, of the structure pointed to by destBitmap.

Returns

SUCCESS The function was successful.
< 1 An error occurred. Refer to Return Codes.

Comments

Typically, this function is used as a preprocessing step when taking images from digital cameras. It changes the image based on a view perspective equation.

It is best to choose input points that are far away from each other.

Call L_ImgKrnDetectDocument to detect the points at the document corners.

Use the results from L_ImgKrnDetectDocument as the input points for the L_ImgKrnPerspectiveCorrectionData structure, which is used by the L_ImgKrnManualPerspectiveCorrection function to correct the perspective of a captured image.

Required DLLs and Libraries

LTIMGKRN
For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

Platforms

Win32, x64, Linux.

Note: All functions with the L_ImgKrn prefix modify the underlying properties of the input BITMAPHANDLE, including but not limited to:

To avoid BITMAPHANDLE property fidelity loss, pass a copy of your BITMAPHANDLE to all L_ImgKrn* functions.

See Also

Functions: L_ImgKrnCopyImage, L_ImgKrnCreateImage, L_ImgKrnCropImage, L_ImgKrnDetectDocument, L_ImgKrnDetectGlare, L_ImgKrnFromYUV, L_ImgKrnInvertImage, L_ImgKrnRotateFlipImage, L_ImgKrnSignalToNoiseRatio
Topics: Raster Image Functions: Doing Geometric Transformations

Example

This example loads a bitmap and applies the manual perspective deskew filter.

L_INT KrnManualPerspectiveCorrectionExample(L_VOID) 
{ 
   L_INT ret; 
   BITMAPHANDLE bitmap;         /* Bitmap handle to hold the loaded image. */ 
   BITMAPHANDLE resultBitmap;   /* Bitmap handle to hold the result image. */ 
 
   /* Load the bitmap */ 
   ret = L_LoadBitmap(MAKE_IMAGE_PATH(TEXT("cannon.jpg")), &bitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if (ret != SUCCESS) 
      return ret; 
 
   L_INT Width = bitmap.Width; 
   L_INT Height = bitmap.Height; 
 
   /* Apply manual perspective deskew filter to move down the top right corner by half of the image height*/ 
   L_ImgKrnPerspectiveCorrectionData data; 
   data.InputPoints[0].x = 0; 
   data.InputPoints[0].y = 0; 
   data.InputPoints[1].x = Width - 1; 
   data.InputPoints[1].y = 0; 
   data.InputPoints[2].x = 0; 
   data.InputPoints[2].y = Height - 1; 
   data.InputPoints[3].x = Width - 1; 
   data.InputPoints[3].y = Height - 1; 
 
   data.MappingPoints[0].x = 0; 
   data.MappingPoints[0].y = 0; 
   data.MappingPoints[1].x = Width - 1; 
   data.MappingPoints[1].y = Height / 2; 
   data.MappingPoints[2].x = 0; 
   data.MappingPoints[2].y = Height - 1; 
   data.MappingPoints[3].x = Width - 1; 
   data.MappingPoints[3].y = Height - 1; 
 
   ret = L_ImgKrnManualPerspectiveCorrection(&bitmap, &data, &resultBitmap, sizeof(BITMAPHANDLE)); 
   if (ret != SUCCESS) 
   { 
      ret = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("Result.BMP")), &resultBitmap, FILE_BMP, 24, 0, NULL); 
 
      L_FreeBitmap(&resultBitmap); 
   } 
 
   //free bitmap 
   L_FreeBitmap(&bitmap); 
 
   return ret; 
} 

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