# Using OpenCL on Image processing. Error in WarpAffine

**URL:** <https://forum.opencv.org/t/using-opencl-on-image-processing-error-in-warpaffine/18125>\
**Category:** Python\
**Tags:** opencl, imgproc\
**Created:** [June 30, 2024, 10:35am UTC](https://forum.opencv.org/t/using-opencl-on-image-processing-error-in-warpaffine/18125 "2024-06-30T10:35:47Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![juan1](https://avatars.discourse-cdn.com/v4/letter/j/bc79bd/32.png) [@juan1](https://forum.opencv.org/u/juan1)\
**Post date:** [June 30, 2024, 10:35am UTC](https://forum.opencv.org/t/using-opencl-on-image-processing-error-in-warpaffine/18125/1 "2024-06-30T10:35:47Z")

</div>

Hi,

First of all saying that I’m not an OpenCv expert…  
As I have been reading using object `UMat` instead of `Mat`, OpenCv will use GPU for image processing instaed of CPU whitch is used when you use `Mat` objects.

My GPU is an integrated Intel UHD Graphics 620

I have been doing operations like rotation or drawing lines and it’s working well. The problem is using `WarpAffine` to make image zoom.

Here is my code and the resulting image. As you can see with `UMat` it’s generating unexpected results.

Thanks for your help

```auto
import os
os.add_dll_directory("C:\\gstreamer\\1.0\\msvc_x86_64\\bin")
 
import cv2 as cv
 
print(cv.getBuildInformation())
 
img_srcFile = "C:\\Users\\usr\\Downloads\\demo.jpg"
 
srcMat = cv.imread(img_srcFile, cv.IMREAD_UNCHANGED)
srcUMat = cv.UMat(cv.imread(img_srcFile, cv.IMREAD_UNCHANGED))
 
cv.imshow("SrcMat", srcMat)
cv.imshow("SrcUMat", srcUMat)
 
height, width = srcMat.shape[:2]
 
point = ((width - 1 )/ 2, (height - 1 )/ 2)
matrixTransfrom = cv.getRotationMatrix2D(point, 0, 1.3)
 
cv.warpAffine(srcMat, matrixTransfrom, (width, height), srcMat)
cv.imshow("SrcMat -> Zoom", srcMat)
 
cv.warpAffine(srcUMat, matrixTransfrom, (width, height), srcUMat)
cv.imshow("SrcUMat -> Zoom", srcUMat)
 
cv.waitKey(0)

```

 ![imagen](https://us1.discourse-cdn.com/flex020/uploads/opencv/original/2X/b/bbf905b9a23203389e9fd06b6a39e3e79ce5c6bc.jpeg)

Here is BuildInformation

```auto
General configuration for OpenCV 4.9.0 =====================================
  Version control: unknown
 
  Platform:
    Timestamp: 2024-04-17T06:33:37Z
    Host: Windows 10.0.19044 AMD64
    CMake: 3.29.1
    CMake generator: Visual Studio 17 2022
    CMake build tool: C:/Program Files/Microsoft Visual Studio/2022/Professional/MSBuild/Current/Bin/amd64/MSBuild.exe
    MSVC: 1939
    Configuration: Debug Release
 
  CPU/HW features:
    Baseline: SSE SSE2 SSE3
      requested: SSE3
    Dispatched code generation: SSE4_1 SSE4_2 FP16 AVX AVX2 AVX512_SKX
      requested: SSE4_1 SSE4_2 AVX FP16 AVX2 AVX512_SKX
      SSE4_1 (18 files): + SSSE3 SSE4_1
      SSE4_2 (2 files): + SSSE3 SSE4_1 POPCNT SSE4_2
      FP16 (1 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 AVX
      AVX (9 files): + SSSE3 SSE4_1 POPCNT SSE4_2 AVX
      AVX2 (38 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2
      AVX512_SKX (8 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2 AVX_512F AVX512_COMMON AVX512_SKX
 
  C/C++:
    Built as dynamic libs?: YES
    C++ standard: 11
    C++ Compiler: C:/Program Files/Microsoft Visual Studio/2022/Professional/VC/Tools/MSVC/14.39.33519/bin/Hostx64/x64/cl.exe (ver 19.39.33523.0)
    C++ flags (Release): /DWIN32 /D_WINDOWS /W4 /GR /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:precise /EHa /wd4127 /wd4251 /wd4324 /wd4275 /wd4512 /wd4589 /wd4819 /MP /O2 /Ob2 /DNDEBUG
    C++ flags (Debug): /DWIN32 /D_WINDOWS /W4 /GR /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:precise /EHa /wd4127 /wd4251 /wd4324 /wd4275 /wd4512 /wd4589 /wd4819 /MP /Zi /Ob0 /Od /RTC1
    C Compiler: C:/Program Files/Microsoft Visual Studio/2022/Professional/VC/Tools/MSVC/14.39.33519/bin/Hostx64/x64/cl.exe
    C flags (Release): /DWIN32 /D_WINDOWS /W3 /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:precise /MP /O2 /Ob2 /DNDEBUG
    C flags (Debug): /DWIN32 /D_WINDOWS /W3 /D _CRT_SECURE_NO_DEPRECATE /D _CRT_NONSTDC_NO_DEPRECATE /D _SCL_SECURE_NO_WARNINGS /Gy /bigobj /Oi /fp:precise /MP /Zi /Ob0 /Od /RTC1
    Linker flags (Release): /machine:x64 /INCREMENTAL:NO
    Linker flags (Debug): /machine:x64 /debug /INCREMENTAL
    ccache: NO
    Precompiled headers: YES
    Extra dependencies:
    3rdparty dependencies:
 
  OpenCV modules:
    To be built: calib3d core dnn features2d flann gapi highgui imgcodecs imgproc ml objdetect photo python3 stitching ts video videoio
    Disabled: world
    Disabled by dependency: -
    Unavailable: java python2
    Applications: tests perf_tests apps
    Documentation: NO
    Non-free algorithms: NO
 
  Windows RT support: NO
 
  GUI: WIN32UI
    Win32 UI: YES
    VTK support: NO
 
  Media I/O:
    ZLib: build (ver 1.3)
    JPEG: build-libjpeg-turbo (ver 2.1.3-62)
      SIMD Support Request: YES
      SIMD Support: NO
    WEBP: build (ver encoder: 0x020f)
    PNG: build (ver 1.6.37)
    TIFF: build (ver 42 - 4.2.0)
    JPEG 2000: build (ver 2.5.0)
    OpenEXR: build (ver 2.3.0)
    HDR: YES
    SUNRASTER: YES
    PXM: YES
    PFM: YES
 
  Video I/O:
    DC1394: NO
    FFMPEG: YES (prebuilt binaries)
      avcodec: YES (58.134.100)
      avformat: YES (58.76.100)
      avutil: YES (56.70.100)
      swscale: YES (5.9.100)
      avresample: YES (4.0.0)
    GStreamer: YES (1.24.2)
    DirectShow: YES
    Media Foundation: YES
      DXVA: YES
 
  Parallel framework: Concurrency
 
  Trace: YES (with Intel ITT)
 
  Other third-party libraries:
    Intel IPP: 2021.11.0 [2021.11.0]
           at: C:/CMake/opencv/opencv/build/3rdparty/ippicv/ippicv_win/icv
    Intel IPP IW: sources (2021.11.0)
              at: C:/CMake/opencv/opencv/build/3rdparty/ippicv/ippicv_win/iw
    Lapack: NO
    Eigen: YES (ver 3.4.0)
    Custom HAL: NO
    Protobuf: build (3.19.1)
    Flatbuffers: builtin/3rdparty (23.5.9)
 
  OpenCL: YES (NVD3D11)
    Include path: C:/CMake/opencv/opencv/3rdparty/include/opencl/1.2
    Link libraries: Dynamic load
 
  Python 3:
    Interpreter: C:/Program Files/Python312/python.exe (ver 3.12.2)
    Libraries: C:/Program Files/Python312/libs/python312.lib (ver 3.12.2)
    numpy: C:/Users/JuanDYB/AppData/Roaming/Python/Python312/site-packages/numpy/core/include (ver 1.26.4)
    install path: C:/Program Files/Python312/Lib/site-packages/cv2/python-3.12
 
  Python (for build): C:/Program Files/Python312/python.exe
 
  Java:
    ant: NO
    Java: NO
    JNI: NO
    Java wrappers: NO
    Java tests: NO
 
  Install to: C:/CMake/opencv/opencv/build/install
-----------------------------------------------------------------

```

---

<div class="post-metadata">

**Author:** ![crackwitz](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/crackwitz/32/14_2.png) [@crackwitz](https://forum.opencv.org/u/crackwitz)\
**Post date:** [June 30, 2024, 5:32pm UTC](https://forum.opencv.org/t/using-opencl-on-image-processing-error-in-warpaffine/18125/2 "2024-06-30T17:32:57Z")

</div>

looks like you’re trying to make it work in-place. and it might have trouble with that.

let it return a new UMat or provide a separate UMat for the result.

if that fixes it, I’d say in-place is the issue. in that case, you should check for existing issues and maybe submit one about this.

make sure that this is reproducible on the latest release, 4.10.

---

<div class="post-metadata">

**Author:** ![juan1](https://avatars.discourse-cdn.com/v4/letter/j/bc79bd/32.png) [@juan1](https://forum.opencv.org/u/juan1)\
**Post date:** [June 30, 2024, 9:03pm UTC](https://forum.opencv.org/t/using-opencl-on-image-processing-error-in-warpaffine/18125/3 "2024-06-30T21:03:21Z")

</div>

Hi,

Thanks for your help. You are all rigth, returning new UMat it works ok.

```auto
dstImg = cv.warpAffine(srcUMat, matrixTransfrom, (width, height))
cv.imshow("SrcUMat -> Zoom", dstImg)

```

I’m in version 4.9. I’ll build 4.10 and check again if it fails. Since I’m using Opencv with Gstreamer backed I have to rebuild from sources.

With regards,

---

<div class="post-metadata">

**Author:** ![crackwitz](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/crackwitz/32/14_2.png) [@crackwitz](https://forum.opencv.org/u/crackwitz)\
**Post date:** [June 30, 2024, 10:25pm UTC](https://forum.opencv.org/t/using-opencl-on-image-processing-error-in-warpaffine/18125/4 "2024-06-30T22:25:31Z")

</div>

eh, you can just install a prebuilt package. no need for gstreamer for this test. create a virtual env and pip install opencv-python

---

<div class="post-metadata">

**Author:** ![juan1](https://avatars.discourse-cdn.com/v4/letter/j/bc79bd/32.png) [@juan1](https://forum.opencv.org/u/juan1)\
**Post date:** [July 2, 2024, 10:00pm UTC](https://forum.opencv.org/t/using-opencl-on-image-processing-error-in-warpaffine/18125/5 "2024-07-02T22:00:12Z")

</div>

Hi!

I have updated to EmguCv 4.9 and also to OpenCv 4.10 and I have tested the issue in both versions.

If seems the issue is there on both versions. As you said using different `UMat` for output I can bypass the bug.

```auto
dstImg = cv.warpAffine(srcUMat, matrixTransfrom, (width, height))
cv.imshow("SrcUMat -> Zoom", dstImg)

```

I have also opened the issue in [Github](https://github.com/opencv/opencv/issues/25853).

---

<div class="post-metadata">

**Author:** ![juan1](https://avatars.discourse-cdn.com/v4/letter/j/bc79bd/32.png) [@juan1](https://forum.opencv.org/u/juan1)\
**Post date:** [July 3, 2024, 12:03pm UTC](https://forum.opencv.org/t/using-opencl-on-image-processing-error-in-warpaffine/18125/6 "2024-07-03T12:03:31Z")

</div>

Hi @crackwitz

Thanks for posting on the issue!

It’s a bad practice to use same `UMat` for input and output?

I’m doing this because I have multiple actions to same frame (WarpAffine, Rotate, DrawLines …)

If I do it with different input and output I have to create more intermediate variables or cotinusly change reference to the input one…

With regards,

---

<div class="post-metadata">

**Author:** ![crackwitz](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/crackwitz/32/14_2.png) [@crackwitz](https://forum.opencv.org/u/crackwitz)\
**Post date:** [July 3, 2024, 5:39pm UTC](https://forum.opencv.org/t/using-opencl-on-image-processing-error-in-warpaffine/18125/7 "2024-07-03T17:39:35Z")

</div>

in-place is suitable for few algorithms.

for most algorithms, “asking for” in-place is impossible, even in principle.

warpAffine is one such function. _if_ it supports in-place, that’ll surely translate to an internal allocation.

you can keep buffers (mats, umats) around for as long as you need. the simplest way forward is to have _two_ buffers, and use them in turn.