If $jpeg_quality doesn't exist, you are effectively asking for zero quality output. If the copied section of source image has little colour or detail, that could result in poor, perhaps even apparently black output.

Use the default or set $jpeg_quality = 100 to see a big difference.

quality 0 versus quality 100.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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In reply to Re: Perl GD imagecopy by BrowserUk
in thread Perl GD imagecopy by natol44

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