Fix: Correct image size calculation for macOS with NSImage

[sejong2401]

Summary

This PR fixes an issue where NSImage was returning incorrect image sizes on macOS.

Issue

• Some images were being compressed to a size smaller than the provided minWidth or minHeight values.
• This is because NSImage.size method returns size information that is screen resolution dependent.
• For example, consider this sample image which has a real size of 1920 x 1200 pixels.
• When compressing this image with a minHeight value of 1000, the resulting image size is 460 x 288, which is incorrect. This issue was observed on a Mac Mini connected to an LG monitor. It is unclear whether the same problem occurs with an iMac or an Apple external display.

Details

• Replaced the NSImage.size method with NSImageRep.pixelsWide and NSImageRep.pixelsHigh to get the actual image size.
• The issue and solution were inspired by the discussion found here.

Testing

• Verified the correct image size is returned.