Resizing app

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Can anyone recommend a Windows program and mac app for resizing photos whilst retaining quality. Photoshop is overkill for this job. I am using Pixresizer but I feel the quality suffers too much. However it is fast. I'll live with a few extra KBs per image if the quality is good.
Any tips about this would be welcome as well.
Photoshop is perfect for this. Ctrl -T then hold shift and resize. The secret is the shift button as it retains the quality.