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Old 08-10-2011, 06:32 AM   #1
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dieda1821 began at the beginning.
Posts: 7
Karma: 10
Join Date: Jan 2011
Device: Sony PRS-650
Plot in epub - resolution problem

Hi all,

Sorry if this problem has already been pointed out.

I would like to embed a plot in an epub file.
The plot is a jpg file hence this seems to be a case equal to embedding an image. Anyhow, I have a strong problem of resolution.
The plot contains written text that must be kept readable inside the e-book (see attached file, 400x208px 72ppi).

I embed the plot as any other image (by hand, no software such as Calibre is involved)

<p class="noindent center">
<img src="images/img7_1.jpg" alt="Scheme" class="plot" />

Where the class .plot would control the size of the image.
Now the problem is that as soon as I use a scalable width for the image (em or %), no matter the value, the quality of the rendered image (tried on ADE and Sony PRS-650) is quite lower than that of the original image and the written text becomes fuzzy, even if I give a width in em that gives out an image as wide as the original one (with ADE on pc).

For some reason, as soon as the width is scalable, the reader somehow reduces the output resolution.

The only solution I found so far is to give a fixed width such as:
<p class="noindent center">
<img src="images/img7_1.jpg" alt="Grafico1" width="400px" class="plot" />


I understand that the resolution problem is very little, in fact by using a picture full of details I never noticed this problem. Anyhow with plots, straight lines + texts + few colors, even a small reduction in resolution affects the readibility.

Is this an intrinsic problem, due to the fact that .svg is the only scalable format that preserve the resolution, or is this a problem of the epub readers that worsen the resolution of images with dim set in em or % ?. In this second case, is there a trick to by-pass the problem ?

Thanks for any possible suggestion.


PS: of course I can also omit the width=400px if that's the real size of the image I want to deal with, which would imply that all the images have been previously properly resized.
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Last edited by dieda1821; 08-10-2011 at 07:13 AM.
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