L_CompareBitmap (original) (raw)

Summary

Compares two images for additions, deletions, and changes and generates an image with the differences highlighted.

Syntax

#include "l_bitmap.h"

L_LTIMGCOR_API L_INT L_CompareBitmap(pReferenceBitmap, pModifiedBitmap, pOutputBitmap, pAlignment, pOptions)

Parameters

pBITMAPHANDLE pReferenceBitmap

Pointer to the reference (original) bitmap.

pBITMAPHANDLE pModifiedBitmap

Pointer to the modified bitmap.

pBITMAPHANDLE pOutputBitmap

Pointer to a bitmap to be populated with the comparison results. See the comments below for more information.

L_MATRIX *pAlignment

Optional pointer to a transformation matrix used to overlay the modified bitmap onto the reference bitmap. If NULL is passed, no transformation will be performed and the images will be aligned to the top-left.

pCOMPAREOPTIONS pOptions

Pointer to the comparison options.

Returns

Comments

The output image (pOutputBitmap) will be 3 bits-per-pixel. The first six entries of its palette are populated from the COMPAREOPTIONS structure (pOptions):

Required DLLs and Libraries

• LTIMGCOR
• 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.

Example

This example shows how to compare an image to its modified and rotated version.

L_INT CompareBitmapExample(L_VOID) { L_INT nRet = SUCCESS; BITMAPHANDLE ReferenceBitmap = { 0 }; // The original image BITMAPHANDLE ModifiedBitmap = { 0 }; // The modified image BITMAPHANDLE OutputBitmap = { 0 }; // The generated image COMPAREOPTIONS Options = { 0 }; // The comparison options L_MATRIX Alignment = { 0 }; // The alignment transformation for the modified image L_RECT RemoveRect = { 0 }; // The region to remove from an image // Load the original image nRet = L_LoadBitmap(MAKE_IMAGE_PATH(TEXT("ocr1.tif")), &ReferenceBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGRORGRAY, NULL, NULL); if (nRet != SUCCESS) goto cleanup; // Use the same image for the "modified" image nRet = L_CopyBitmap(&ModifiedBitmap, &ReferenceBitmap, sizeof(BITMAPHANDLE)); if (nRet != SUCCESS) goto cleanup; // Remove the last paragraph of the reference image L_Rect_Make(&RemoveRect, 290, 2470, 1930, 360); nRet = L_SetBitmapRgnRect(&ReferenceBitmap, NULL, &RemoveRect, L_RGN_SET); if (nRet != SUCCESS) goto cleanup; nRet = L_FillBitmap(&ReferenceBitmap, RGB(255, 255, 255)); if (nRet != SUCCESS) goto cleanup; nRet = L_FreeBitmapRgn(&ReferenceBitmap); if (nRet != SUCCESS) goto cleanup; // Remove the title from the modified image L_Rect_Make(&RemoveRect, 290, 300, 810, 110); nRet = L_SetBitmapRgnRect(&ModifiedBitmap, NULL, &RemoveRect, L_RGN_SET); if (nRet != SUCCESS) goto cleanup; nRet = L_FillBitmap(&ModifiedBitmap, RGB(255, 255, 255)); if (nRet != SUCCESS) goto cleanup; nRet = L_FreeBitmapRgn(&ModifiedBitmap); if (nRet != SUCCESS) goto cleanup; // Rotate the modified image for demonstration (angle measured in hundredths of a degree) nRet = L_RotateBitmap(&ModifiedBitmap, 340 * 100, ROTATE_RESIZE, RGB(0, 0, 0)); if (nRet != SUCCESS) goto cleanup; // Update the transformation to align/reverse the above rotation L_Matrix_Identity(&Alignment); L_Matrix_Translate(&Alignment, -ModifiedBitmap.Width * 0.5, -ModifiedBitmap.Height * 0.5); L_Matrix_Rotate(&Alignment, 20.0); L_Matrix_Translate(&Alignment, ReferenceBitmap.Width * 0.5, ReferenceBitmap.Height * 0.5); // Setup the comparison options Options.uStructSize = sizeof(COMPAREOPTIONS); Options.uThreshold = 0; // The images are bitonal, no need for measuring color distance Options.crReferenceBackground = RGB(255, 255, 255); // White Options.crReferenceForeground = RGB(0, 0, 0); // Black Options.crModifiedBackground = RGB(255, 255, 255); // White Options.crModifiedForeground = RGB(0, 0, 0); // Black Options.crOutputExternal = RGB(128, 128, 255); // Light blue Options.crOutputBackground = RGB(255, 255, 255); // White Options.crOutputMatch = RGB(64, 64, 64); // Dark gray Options.crOutputAddition = RGB(0, 255, 0); // Green Options.crOutputDeletion = RGB(255, 0, 0); // Red Options.crOutputChange = RGB(255, 255, 0); // Yellow // Compare the images nRet = L_CompareBitmap(&ReferenceBitmap, &ModifiedBitmap, &OutputBitmap, &Alignment, &Options); if (nRet != SUCCESS) goto cleanup; // Save the results nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("CompareBitmap_Output.png")), &OutputBitmap, FILE_PNG, 0, 0, NULL); if (nRet != SUCCESS) goto cleanup; // Save the two input images, for reference nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("CompareBitmap_Reference.png")), &ReferenceBitmap, FILE_PNG, 0, 0, NULL); if (nRet != SUCCESS) goto cleanup; nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("CompareBitmap_Modified.png")), &ModifiedBitmap, FILE_PNG, 0, 0, NULL); if (nRet != SUCCESS) goto cleanup; cleanup: // Free the loaded images if (ReferenceBitmap.Flags.Allocated) L_FreeBitmap(&ReferenceBitmap); if (ModifiedBitmap.Flags.Allocated) L_FreeBitmap(&ModifiedBitmap); if (OutputBitmap.Flags.Allocated) L_FreeBitmap(&OutputBitmap); return nRet; }

Reference, Modified, and Output Images

The following images are generated when the example is run:

• Reference Image
  
• Modified Image
  
• Output Image