Fix banding artifacts in macOS viewer (#1977) #12

Job	Run time
Python SDist	0s
Build (Linux_GCC_9_Python37, ubuntu-20.04, gcc, 9, 3.7, -DMATERIALX_BUILD_SHARED_LIBS=ON)	10m 5s
Build (Linux_GCC_12_Python311, ubuntu-22.04, gcc, 12, 3.11, ON)	18m 17s
Build (Linux_GCC_12_Python311_Static_Monolithic, ubuntu-22.04, gcc, 12, 3.11, -DMATERIALX_BUILD_S...	11m 46s
Build (Linux_GCC_14_Python312, ubuntu-24.04, gcc, 14, 3.12, ON, -DCMAKE_EXPORT_COMPILE_COMMANDS=ON)	20m 11s
Build (Linux_GCC_CoverageAnalysis, ubuntu-22.04, gcc, None, None, ON, -DMATERIALX_COVERAGE_ANALYS...	12m 3s
Build (Linux_Clang_10_Python37, ubuntu-20.04, clang, 10, 3.7, -DMATERIALX_BUILD_SHARED_LIBS=ON)	9m 24s
Build (Linux_Clang_18_Python312, ubuntu-24.04, clang, 18, 3.12, ON, ON)	11m 40s
Build (MacOS_Xcode_13_Python37, macos-12, xcode, 13.1, -DMATERIALX_BUILD_SHARED_LIBS=ON, 3.7)	15m 19s
Build (MacOS_Xcode_14_Python311, macos-14, xcode, 14.3, 3.11)	6m 10s
Build (MacOS_Xcode_15_Python312, macos-14, xcode, 15.0, 3.12, ON)	6m 51s
Build (MacOS_Xcode_DynamicAnalysis, macos-14, xcode, 15.0, None, ON, -DMATERIALX_DYNAMIC_ANALYSIS...	12m 49s
Build (iOS_Xcode_15, macos-14, xcode, 15.0, None, -DMATERIALX_BUILD_IOS=ON -DCMAKE_OSX_SYSROOT=`x...	1m 35s
Build (Windows_VS2019_Win32_Python37, windows-2019, x86, 3.7, -G "Visual Studio 16 2019" -A "Win3...	12m 39s
Build (Windows_VS2022_x64_Python311, windows-2022, x64, 3.11, -G "Visual Studio 17 2022" -A "x64"...	11m 20s
Build (Windows_VS2022_x64_Python312, windows-2022, x64, 3.12, -G "Visual Studio 17 2022" -A "x64"...	9m 57s
Python Wheels	0s
	2h 50m 6s

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