Dw 30 optimize extract alpha data and prepare byte array

[ikkyuland]

Title

slightly improve speed of ExtractAlphaData and PrepareByteArray

Description

• use array and index to increase speed of ExtractAlphaData
• use BlockCopy to increase speed PrepareByteArray

Fixes
DW-30

Type of change

Please select the relevant option by placing an 'x' inside the brackets, like this: [x].

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 🏗️ Internal/structural update (non-breaking change that improves code quality, organization, or performance)
• 📚 This change requires a documentation update
• 🚀 DevOps build chain modification for release
• 🤖 DevOps build chain modification for CI

How Has This Been Tested?

all test passes,

Checklist:

Please run through the checklist as much as possible and mark the items completed by placing an 'x' inside the brackets, like this: [x].

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• [] My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have successfully run all unit tests on Windows
• I have successfully run all unit tests on Linux

Additional Context

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