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I am using php and fpdf to generate a pdf. How can I scale a 400 pixel high image to fit in a 300 point high space? The dimensions are just examples, the image and available space are dynamic.

maddogandnoriko
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2 Answers2

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If you want to fit 400 pixels in 300 points, then your resizing factor would simply be 300 / 400 = 0.75. You need to put each pixel in 0.75 of a point.

But there is another story you should know: Each point is 1/72 of an inch. and how many pixels make 1 inch is a matter of choice.

All images have a property called DPI: dots per inch. It specifies how many pixels are there for each inch of the picture. So if you want to convert a 400px * 400px picture to a (say) 96 dpi image, your resizing factor will be 400 / ((72 / 96) * 400). 72 here is for converting inches to points.

Abel Callejo
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Hossein
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  • Agreed, I explained it badly. I think your first sentence answers my question. In my original question I did not know wheteher the user was using 72dpi or 96dpi(or anything else). – maddogandnoriko Jan 04 '12 at 18:11
  • I think it is how many pixels make up an inch is a matter of choice. – maddogandnoriko Jan 04 '12 at 18:14
  • You're right, I edited. But imagine a world where a single pixel is bigger than an inch, then we can talk about how many inches make one pixel. Why not? :) – Hossein Jan 04 '12 at 18:19
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You can resize the picutre first with imagecopyresampled.

-> Basic Example
-> Adding image to pdf

Tobias
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  • I can resize the image but I do not know how to convert pixels to points, not knowing what the users system is set to. – maddogandnoriko Jan 04 '12 at 17:43
  • What's the problem in using image? – Tobias Jan 04 '12 at 17:48
  • If the image is smaller than 300 points I do not want resize it. If it is larger I need to resize it. And all I have is pixels to test that. I also may need to resize X or Y depending on if the image is taller or wider. I see 96 dpi in the image function, should I covert using 96dpi? Or is that an assumption I should not make? – maddogandnoriko Jan 04 '12 at 17:58