It seems AccelerateResizeImage was not enabled in ImageMagick 7. I just committed a change to fix this for the next release of Magick.NET.
AccelerateResizeImage will only be used if the image contains an alpha channel. ImageMagick 6 always has 4 channels per pixel and the OpenCL code for ImageMagick 7 also expects this. This will be changed in the future but I don't know when this will be done. To add an alpha channel to your jpeg file use: MagickImage.Alpha(AlphaOption.On);
The next release of Magick.NET will probably be in the end of February. Contact me through CodePlex if you want a development build to test the OpenCL acceleration.
AccelerateResizeImage will only be used if the image contains an alpha channel. ImageMagick 6 always has 4 channels per pixel and the OpenCL code for ImageMagick 7 also expects this. This will be changed in the future but I don't know when this will be done. To add an alpha channel to your jpeg file use: MagickImage.Alpha(AlphaOption.On);
The next release of Magick.NET will probably be in the end of February. Contact me through CodePlex if you want a development build to test the OpenCL acceleration.