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| ID | Project | Category | View Status | Date Submitted | Last Update | ||||
| 0011613 | VTK | (No Category) | public | 2010-12-16 09:29 | 2012-12-12 12:19 | ||||
| Reporter | John Stark. | ||||||||
| Assigned To | David Gobbi | ||||||||
| Priority | normal | Severity | minor | Reproducibility | always | ||||
| Status | closed | Resolution | fixed | ||||||
| Platform | OS | OS Version | |||||||
| Product Version | |||||||||
| Target Version | Fixed in Version | 5.10.0 | |||||||
| Summary | 0011613: vtkOpenGLImageActor hangs if image is empty. | ||||||||
| Description | When an empty image is passed to the vtkOpenGLImageActor, the MakeDataSuitable method can enter an infinite loop, and hang. The problem only occurs when the image returns it's extents as [0, -1, 0, -1, 0, -1]. In this case, the xsize is inferred to be -1, and the loop to find the next power of 2 falls into an infinite loop. | ||||||||
| Additional Information | The problem occurs here : xsize = ext[xdim*2+1] - ext[xdim*2] + 1; // xsize and ysize must be a power of 2 in OpenGL xs = static_cast<unsigned short>(xsize); while (!(xs & 0x01)) { xs = xs >> 1; } If xs is zero, the loop never terminates. Please can you add an additional test that both xsize and ysize are > zero : diff --git a/Rendering/vtkOpenGLImageActor.cxx b/Rendering/vtkOpenGLImageActor.cxx index 172b82a..79ee1a8 100644 --- a/Rendering/vtkOpenGLImageActor.cxx +++ b/Rendering/vtkOpenGLImageActor.cxx @@ -154,9 +154,12 @@ unsigned char *vtkOpenGLImageActor::MakeDataSuitable(int &xsize, int &ysize, xsize = ext[xdim*2+1] - ext[xdim*2] + 1; // xsize and ysize must be a power of 2 in OpenGL xs = static_cast<unsigned short>(xsize); - while (!(xs & 0x01)) + if (xsize > 0) { - xs = xs >> 1; + while (!(xs & 0x01)) + { + xs = xs >> 1; + } } if (xs == 1) { @@ -170,9 +173,12 @@ unsigned char *vtkOpenGLImageActor::MakeDataSuitable(int &xsize, int &ysize, ysize = (this->ComputedDisplayExtent[ydim*2+1] - this->ComputedDisplayExtent[ydim*2] + 1); ys = static_cast<unsigned short>(ysize); - while (!(ys & 0x01)) + if (ysize > 0) { - ys = ys >> 1; + while (!(ys & 0x01)) + { + ys = ys >> 1; + } } // yes it is a power of two already if (ys == 1) | ||||||||
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(0024208) David Gobbi (developer) 2010-12-16 10:23 |
Those loops should not be there at all, there is an easier way to check if the dimensions are a power of two: // check whether dimensions are a power of two if (xsize > 0 && (xsize & (xsize-1)) == 0 && ysize > 0 && (ysize & (ysize-1)) == 0) { } Subtracting one from a non-zero value causes the lowest set bit to be cleared. If the lowest set bit is the only set bit (as is the case only for a power-of-two), then all set bits will be cleared, and (x & (x-1)) will be zero. Therefore, (xsize & (xsize-1)) == 0 if and only if xsize is a power of two or is zero. I have pushed commit 6cd830040010eef56af491906a0f58b8cc3a367d to fix this bug. |
| Notes |
| Issue History | |||
| Date Modified | Username | Field | Change |
| 2010-12-16 09:29 | John Stark. | New Issue | |
| 2010-12-16 09:55 | David Gobbi | Assigned To | => David Gobbi |
| 2010-12-16 09:55 | David Gobbi | Status | backlog => tabled |
| 2010-12-16 10:23 | David Gobbi | Note Added: 0024208 | |
| 2010-12-16 10:37 | David Gobbi | Status | tabled => @80@ |
| 2010-12-16 10:37 | David Gobbi | Resolution | open => fixed |
| 2012-12-12 12:19 | David Gobbi | Status | customer review => closed |
| 2012-12-12 12:19 | David Gobbi | Fixed in Version | => 5.10.0 |
| Issue History |
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