High Resolution Bitmap Export (perhaps via slicing)

[jpavel]

Hello all,

I'm planning to print a sizable, high resolution poster, and I'm going to provide the printer with a large TIFF or PNG image (about 6000x6000). I was considering two options:

1. Exporting the large bitmap directly from Xara - but can it handle resolutions that high?

2. Export the picture in blocks of 1000x1000 or so, and then combine them in Photoshop or Gimp.
In this case, I'd have to slice up the picture for the export, not in the sense of named slicing, but just in rectangular pieces. Any recommendations on how to do this so that there aren't any misalignments at the edges?

Thanks!
Jesse

[mwenz]

1. 6000 x 6000 what? Pixels?
2. Create 1000 x 1000 whatever squares, slice the image. With one piece selected, export selected. Rinse and repeat for each piece.

But, why not export a PDF of the whole?

[jpavel]

1. Yup, 6000x6000 pixels.
2. I've found that when exporting to PDF, when using certain features like bitmap transparencies scaled to very small dimensions, one would see artifacts when viewing the result. Also, thin lines are sometimes printed thicker than specified, depending on the PDF rendering settings at print time.

It's not an image that I'm slicing up, but the Xara drawing as a whole, so if I slice (shapes), outlines are modified.

Thanks,
Jesse

[mwenz]

I really don't know what to suggest with the information given--I haven't had the issue when exporting to PDF you mention.

But for slicing and dicing, you can:
Group your design drawing.
Make as many copies of you drawing as you need tiled.
Make and arrange rectangles so they abut each other in the tile pattern you desire.
Send on rectangle below the top group of your drawing.
The rectangle will still be selected, now select the topmost grouped drawing.
Hit Q
Repeat for each tile.

Other than that, I would need a sample of your drawing. As long as your bitmap effects are set to high resolution, perhaps use PDF Reader Version 8 for the output type, it should be good.

Take care, Mike

[Albacore]

Why not tile it as Mike has suggested, most printer drivers will allow this and you can print them to your printer driver and save them, then do your worst in PS. There are other methods which I have used in vinyl banners and that is Posterize at least that what it was once called: http://www.blockposters.com/

Like Mike again I would have chosen the PDF method which works for me. I thought that the line thickness was only a problem if you used a size under 0.5pt when exporting to PDF, might Google that point. Never had gradients or as you mention transparencies becoming smaller would check your advance settings in your Objects tab, use Custom DPI and make it a denominator from scale so that you have at least 120 DPI after scaling up. Have a try and at least you can check it in PS if you have enough memory to load PDF or better if you have Acro. Pro.

[jpavel]

Thanks for your replies, mwenz and Albacore.

I tried making a tile pattern and exporting in pieces that way, but Xara likes to put a very thin band of background around each exported slice. If need be, I could edit the pieces together, but would take a little extra effort.

However, while I had problems exporting large PNG's, I tried exporting as a 24-bit, LZW-compressed TIFF, and was able to create a 50 MP image without a hitch, just waiting for my CPU to churn a bit.

Best,
Jesse

[PhilM]

How about this method, which is high-res, non-destructive of your document and avoids the anti-aliased edges:

* Create a new layer on top of all others called "Slice".
* Draw the tiling rectangles on that layer, ensuring that they are all snapped together exactly.
* Make all the rectangles on that layer have no fill and no line colour
* Now select one of them. This is tricky when they are invisible but there are various ways to do it. Either go down to outline mode temporarily to clicl on the outline or use the Tab key in the selector Tool.
* Now choose "Export...", choose PNG, choose Area to save: "Selection", choose Colour depth: "True colour", choose "maintain screen anti-aliasing", and set whatever resolution you like.
* Export and repeat for all the other rectangles on the "Slice" layer.

The resulting high-res bitmaps should fit together perfectly without any edge artefacts.

Also check out Imagemap exporting and the "Save each layer to a file of its own" option to help automate the process a bit.

One more thing: It's a good idea to make sure that your tiling rectangles are a whole number of pixels wide and high in the export resolution. E.g. if you are going to export at 300dpi, make the tiling rectangles be a multiple of whole inch sizes.

Phil

[Acorn]

* Make all the rectangles on that layer have no fill and no line colour
Phil

I "discovered" this approach a time back so it's great it's validated here.
Thanks,
Acorn

[jpavel]

Thanks for more detail on the slicing method you use.

I tried it (and attached Test Slice.xar), and have an odd visual artefact.

You can see in odd_assembly.png that there is a strange distortion in one of the frames, which causes a misalignment running from the cat's nose downward
.
I've also uploaded a zip of the 4 individual slices that went into odd_assembly, exported from the four squares in the Slice layer at 300dpi.

If you could take a look and let me know my error (or confirm a bug), I'd most appreciate it.

~Jesse

[mwenz]

Your slice rectangles are not whole pixels.