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I read that exposure is the amount of light allowed to fall on each area unit of a photographic medium (photographic film or image sensor) during the process of taking a photograph, according to wiki. I am not from image processing background. So,I am still confused about it.

But I cannot find any tutorial on exposure adjustment using php. Is there a way to develop exposure adjustment function in php gd? Can anyone advise? Thank you.

ATZ
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1 Answers1

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You should adjust brightness, not exposure. Once a JPG or BMP is already made, you can just brighten-up a pixel. The term "exposure" is properly used only while taking a digital image or developing negatives (analogue or digital).

GD has imagefilter function, you should probably use the IMG_FILTER_BRIGHTNESS filter type.

Vanja D.
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  • Thank. I have already adjusted brightness using Img-filter_brightness. But I am wondering whether we can adjust exposure in image editing tool like this website does.https://apps.facebook.com/picmonkey/ So, it means exposure is only for taking photos but not for image editing tools? – ATZ Oct 02 '12 at 07:48
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    Well, many tools say "exposure" when they are actually just changing a photo's brightness and contrast levels. So you should try different combinations of filters and possibly even writing your own. – Vanja D. Oct 02 '12 at 11:51