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Old 03-06-2007, 05:47 AM   #1
adinb
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Question Rendered Image Size in Picture Mode (S/M/L)?

My apologies if I'm asking a stupid question---to me its one of the questions that I would expect to be in a FAQ, but I can't find it anywhere.

What size does the PRS-500 render images in picture mode?

With different size images, it seems to always be resizing to a constant image size in S/M/L (Landscape different than Portrait). Whether the image is 1200x900 or 2075x1826 or even larger, it seems do be downsized to an unknown target size.

The zoom-around in "L" in picture mode (landscape) seems to be somewheres around 1200 pixels (800x1.5 zoom?), but I'm not totally sure.

Anyone actually know the pixel counts?
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Old 03-06-2007, 06:39 AM   #2
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The screen is 800x600 pixels, so presumably it's somewhere around that.
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Old 03-06-2007, 06:42 AM   #3
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Here's the formula it uses for scaling images:
width = screenwidth + zoom * screenwidth / 2
height = screenheight + zoom * screenheight / 2
Where zoom is 0 for S, 1 for M and 2 for L.
As for screenwidth and screenheight, I _think_ it's 600x770, but I'm not 100% sure.
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Old 03-06-2007, 06:43 AM   #4
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In large picture mode you scroll around the picture--from eyeballing it, it looks like you get about 2/3 the image in any direction at a time. I'm just trying to figure out what the downsample resolution is, so that I can optimize converted PDFs accordingly.
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Old 03-06-2007, 07:00 AM   #5
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@Igorsk--

Here's the odd thing. I took a pdf, converted it at 166 dpi, so
2075x3652 (and I tried 83 dpi, so 1037x1826). Just testing, i tried
converting the PDF at 332 dpi, so the resulting images were 4150 x
7304. I cut both set of images in half. (so really 1037x913,
2075x1826 and 4150x3652).

Each one of the images ended up looking the exact same. Small, medium,
and Large created the same amount of scrolling-around space, and the
text in the pdf was dithered beyond what was done on the computer
(previewed in the sony connect reader).

Anyways, this all leads me to believe that on pictures that are larger than a certain size get downsized--just like if I don't cut the rasterized pdf images in half, it won't let me scroll around the whole page even in "large" mode--it stays zoomed out enough that you can't read the text.

So, I think the formula applies for smaller images, but I think there are hardset limits for larger images.


So, its doing some funky resizing, and I *really* want to get the DPI
that I should convert PDFs nailed.

-adin

Last edited by adinb; 03-06-2007 at 07:04 AM.
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Old 03-06-2007, 07:34 AM   #6
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Well, the formula I provided is for the image viewer, not PDF (your original question didn't mention PDF at all). AFAIK PDF has only two sizes: full page and content only.
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Old 03-06-2007, 04:38 PM   #7
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@igorsk --


I am talking about images--I'm converting PDF's to JPEGS because of the extra zoom capability--and matching up DPI/Aspect Ratio, etc is critical to making a "readable" oversized (12.5"x22") image. This is only tangentially related to PDF's -- they're just pictures on the e-reader. I only mentioned PDF because of my use case--keeping detail through the conversion.

It may be easier to just show you what I'm talking about, I'm uploading some examples for you to look at. I rendered them at 100% jpeg quality so that jpeg artifacting wouldn't be an issue.

Here is a sampling of the original PDF's. (4 pages, 2.9MB)

View the following on your ereader in Large image mode:

Here is a sampling of the images at 83 DPI (8 pages, 1037x913 each,7MB)
Here is a sampling of the images at 166 DPI (8 pages, 2075x1826 each, 21MB)
Here is a sampling of the images at 332 DPI (8 pages, 4150x3652 each, 57.3MB)

Notice that with each example, the images double in size, yet you're not having to scroll around twice as far-the same amount of the image is shown, regardless of the original image size.

So what image size is the e-reader downsampling to? Because that would be the resolution that you could get the greatest detail in an image.

So, this question can also be asked in another way--what's the optimal size to use in JAP when exporting to jpeg? 1600x1408? 2075x1826? Or are the images to large, causing to e-reader to do its own downsampling, causing artifacts in the image?
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