如何查询raster image的像素值

LoveArx

Issue
How do I find out the pixel value in a raster image inserted into an AutoCAD
drawing.

Solution
To convert a coordinate in the world coordinates system, you can use the AcDbRasterImage::getPixelToModelTransform() function. Then you will need to use the Atil SDK to access the individual pixels of the image.

Following code demonstrates how to do it:

1. void AsdkGetPixelValue()
   
2. {
   
3. ads_name name;
   
4. ads_point pt;
   
5. Acad::ErrorStatus es;
   
6. 
   
7. if (acedEntSel(L"\nSelect a Raster Image : ", name, pt) != RTNORM)
   
8. {
   
9.   return;
   
10. }
    
11. 
    
12. AcDbObjectId objId;
    
13. acdbGetObjectId(objId, name);
    
14. 
    
15. 
    
16. AcDbEntity * pEnt;
    
17. es = acdbOpenObject(pEnt, objId, AcDb::kForRead);
    
18. AcDbRasterImage *pRaster = AcDbRasterImage::cast(pEnt);
    
19. if (pRaster == NULL)
    
20. {
    
21. pEnt->close();
    
22.   return;
    
23. }
    
24. 
    
25. 
    
26. // Get pixel value
    
27. AcGeVector2d imgSize = pRaster->imageSize();
    
28. AcGeMatrix3d mat;
    
29. es = pRaster->getPixelToModelTransform(mat);
    
30. AcGePoint3d modpt;
    
31. 
    
32. if (acedGetPoint(NULL, L"\nSelect point in image : ", asDblArray(modpt)) != RTNORM)
    
33. {
    
34.   return;
    
35. }
    
36. 
    
37. 
    
38. AcGePoint3d pixpt(0,0,0);
    
39. pixpt = mat.inverse() * modpt;
    
40. 
    
41. 
    
42. int x = (int)pixpt[0];
    
43. int y = (int)pixpt[1];
    
44. 
    
45. 
    
46. if ((x > imgSize.x) || (x < 0) || (y > imgSize.y) || (y < 0))
    
47. {
    
48. acutPrintf(L"\n*** This point is not within the image ***\n");
    
49. pRaster->close();
    
50.   return;
    
51. }
    
52. else
    
53. {
    
54. acutPrintf(L"\nPixel Selected: (%d, %d)", x, y);
    
55. }
    
56. 
    
57. 
    
58. // Get a copy of the image from the rastier image def
    
59. AcDbRasterImageDef * pDef;
    
60. 
    
61. es = acdbOpenObject(pDef, pRaster->imageDefId(), AcDb::kForWrite);
    
62. Atil::Image* pImg = pDef->imageCopy();
    
63. 
    
64. 
    
65. pRaster->close();
    
66. pDef->close();
    
67. 
    
68. 
    
69. 
    
70. // Find out bits per pixel of image
    
71. Atil::ImageContext* imgContext = pImg->createContext(Atil::ImageContext::kRead, pImg->size(), Atil::Offset(0,0));
    
72. 
    
73. Atil::DataModelAttributes::BitsPerPixel bpp = pImg->dataModel().bitsPerPixel();
    
74. 
    
75. // Show pixel value
    
76. switch (bpp)
    
77. {
    
78. case Atil::DataModelAttributes::BitsPerPixel::k1:
    
79. acutPrintf(L"\nPixel value = %u\n", imgContext->get1(x,y));
    
80.   break;
    
81. case Atil::DataModelAttributes::BitsPerPixel::k8:
    
82. acutPrintf(L"\nPixel value = %u\n", imgContext->get8(x,y));
    
83.   break;
    
84. case Atil::DataModelAttributes::BitsPerPixel::k16:
    
85. acutPrintf(L"\nPixel value = %u\n", imgContext->get16(x,y));
    
86.   break;
    
87. case Atil::DataModelAttributes::BitsPerPixel::k32:
    
88. acutPrintf(L"\nPixel value = %u\n", imgContext->get32(x,y));
    
89.   break;
    
90. case Atil::DataModelAttributes::BitsPerPixel::k64:
    
91. acutPrintf(L"\nPixel value = %u\n", imgContext->get64(x,y));
    
92.   break;
    
93. default:
    
94. acutPrintf(L"\n*** This color scale is not supported. ***\n");
    
95. }
    
96. 
    
97. 
    
98. //Clean up
    
99. delete imgContext;
    
100. delete pImg;
     
101. 
     
102. return;
     
103. }
     

void AsdkGetPixelValue()<br /> {<br /> ads_name name;<br /> ads_point pt;<br /> Acad::ErrorStatus es;<br /> <br /> if (acedEntSel(L"\nSelect a Raster Image : ", name, pt) != RTNORM)<br /> {<br />   return;<br /> }<br /> <br /> AcDbObjectId objId;<br /> acdbGetObjectId(objId, name);<br /> <br /> <br /> AcDbEntity * pEnt;<br /> es = acdbOpenObject(pEnt, objId, AcDb::kForRead);<br /> AcDbRasterImage *pRaster = AcDbRasterImage::cast(pEnt);<br /> if (pRaster == NULL)<br /> {<br /> pEnt->close();<br />   return;<br /> }<br /> <br /> <br /> // Get pixel value<br /> AcGeVector2d imgSize = pRaster->imageSize();<br /> AcGeMatrix3d mat;<br /> es = pRaster->getPixelToModelTransform(mat);<br /> AcGePoint3d modpt;<br /> <br /> if (acedGetPoint(NULL, L"\nSelect point in image : ", asDblArray(modpt)) != RTNORM)<br /> {<br />   return;<br /> }<br /> <br /> <br /> AcGePoint3d pixpt(0,0,0);<br /> pixpt = mat.inverse() * modpt;<br /> <br /> <br /> int x = (int)pixpt[0];<br /> int y = (int)pixpt[1];<br /> <br /> <br /> if ((x > imgSize.x) || (x < 0) || (y > imgSize.y) || (y < 0))<br /> {<br /> acutPrintf(L"\n*** This point is not within the image ***\n");<br /> pRaster->close();<br />   return;<br /> }<br /> else<br /> {<br /> acutPrintf(L"\nPixel Selected: (%d, %d)", x, y);<br /> }<br /> <br /> <br /> // Get a copy of the image from the rastier image def<br /> AcDbRasterImageDef * pDef;<br /> <br /> es = acdbOpenObject(pDef, pRaster->imageDefId(), AcDb::kForWrite);<br /> Atil::Image* pImg = pDef->imageCopy();<br /> <br /> <br /> pRaster->close();<br /> pDef->close();<br /> <br /> <br /> <br /> // Find out bits per pixel of image<br /> Atil::ImageContext* imgContext = pImg->createContext(Atil::ImageContext::kRead, pImg->size(), Atil::Offset(0,0));<br /> <br /> Atil::DataModelAttributes::BitsPerPixel bpp = pImg->dataModel().bitsPerPixel();<br /> <br /> // Show pixel value<br /> switch (bpp)<br /> {<br /> case Atil::DataModelAttributes::BitsPerPixel::k1:<br /> acutPrintf(L"\nPixel value = %u\n", imgContext->get1(x,y));<br />   break;<br /> case Atil::DataModelAttributes::BitsPerPixel::k8:<br /> acutPrintf(L"\nPixel value = %u\n", imgContext->get8(x,y));<br />   break;<br /> case Atil::DataModelAttributes::BitsPerPixel::k16:<br /> acutPrintf(L"\nPixel value = %u\n", imgContext->get16(x,y));<br />   break;<br /> case Atil::DataModelAttributes::BitsPerPixel::k32:<br /> acutPrintf(L"\nPixel value = %u\n", imgContext->get32(x,y));<br />   break;<br /> case Atil::DataModelAttributes::BitsPerPixel::k64:<br /> acutPrintf(L"\nPixel value = %u\n", imgContext->get64(x,y));<br />   break;<br /> default:<br /> acutPrintf(L"\n*** This color scale is not supported. ***\n");<br /> }<br /> <br /> <br /> //Clean up<br /> delete imgContext;<br /> delete pImg;<br /> <br /> return;<br /> }<br />

Please note that this code incorporates only minimal error checking.