I'm making a poster using pictures.

All that's on the poster are 6 jpg pictures, each about 500k, so a total of 3M.

When I export a png file, it's about 13M, which is too big for me to upload to the printer.

I have what I think is partial workaround, by uploading the large png to an online png->jpg conveter, which returns a file that is about 3M, but with no transparency.

What causes the png file to be much larger than its contents? Is there a way to generate a smaller png file in Inkscape?

Many thanks.

Look in the Export PNG dialog for the DPI setting. Make sure it's set to 96.

If that doesn't solve it, select one of the photos, and notice the Width and Height on the Selection tool control bar. Next notice what the status bar says. It tells the real size of the photo.

For some reason which I don't understand, whenever I import raster images, they are smaller than they are supposed to be. I always have to scale them to their correct size, after I import them. If that happened to you, then what you are looking at and measuring in Inkscape is much smaller than what their real size is. And when you go to print, it prints to the real size.

So the fix will be to scale the photos to their correct size, before you do whatever else you need to do.

Let us know how it goes.

Thanks for the explanation.

I had resized the photos before I imported them, so I don't think that's my problem.

However. I was going for an output resolution of 200dpi to print.

I tried lowering the dpi to 96. It made the file a little smaller, but not much.

I'll fiddle with it some more, but do I want to leave the dpi at 96 even for a print document?

Thanks.

Are the JPGs photographs? Well, as I understand the JPG format is good for photographs, PNGs is a good for ScreenShots and others but not necessarily for photographs. So, I am not surprised that the combined image gets much larger. Just tested with a 740 kB JPG photograph... it becomes a 4 MB PNG, even with compression.
Do you explicitly need a PNG as output? Have you tried exporting your poster (i.e. "save a copy...") as PDF? How large does it get? I hope your printer also can print PDFs.

Dont-export-to-png-if-you-want-to-print-it.

Save as pdf.

...

Yet another topic on resolution.
By exporting a drawing/part of a drawing you (re-)rendering an area. It's not the same content as the image embedded.
Even if no modifications were taken. You can only export to png images. Which by default has an alpha channel you can't switch off.
Jpegs don't have that, and they use a rather different way of storing the pixel information.
A different way to compress the file.

Dpi corresponds to pixels/dots per inch. Do we know the size you want your exported image to be printed?
Do we know how large your exported area is in real word units in your document?
No.
If you describe the desired output size AND desired printing resolution, then you could calculate the necessary image size in pixels.
What export resolution would lead to that pixel size?
All depends on how large you scale the image in your document.
And yet you want 200 dpi to be embedded as well into the exported file.
Then, you would need to scale your embedded images accordingly.

After that, it's all about the printer to handle the image.
Can you print a raster image true to its scale? On win, printing only brings up a useless setting panel.

Just no.


Instead, create your document by using real word units. mm, inch, whatever goes, you can draw in true scale for most images to be printed.
Save as pdf.
That way the embedded raster images are not re-rendered, but embedded in their original formats. That means you can preserve the jpeg compression, and maybe even get a smaller size due to the pdf's own compressing.
Print the pdf outside inkscape. Pdf readers are available for free, foxit or acrobat reader are the most common. They have the option to print the document in its original size. End of story, you don't need to calculate pixel sizes and resolutions.


For further explanation check this topic.


(Sorry for the harsh language.)

Hi.

Here's what I (think) I discovered:

If you once had a file imported of a large size, even when you delete it the png stays the big size. I had started my document with photos that were too big and then deleted them. But that doesn't seem to make them go away when exporting a png.

I tried the clean up document option on the file menu and it had no impact on this.

This printer can't take pdf, but I can make my workaround work.

Thanks for your help.

Just for completeness:

if you describe the desired output size AND desired printing resolution, then you could calculate the necessary image size in pixels.
What export resolution would lead to that pixel size?

Output is to be 20 inches by 30 inches at 200dpi

I set the document size to 4000x6000px. Is this where my error? What is right?

All depends on how large you scale the image in your document.

I have scaled the images to be 990 x 1320 , which gives me filesizes of 300k-500k I'm using six: 3 rows of 2

Thanks for the explanations

By re-rendering your image at a different resolution you won't get more details but end up with a "smudged" image.

20 inch / 30 inch = 4000 px / 6000 px @ 200 dpi.
Document size is just about right for exporting at inkscape's native (90) 96 dpi resolution.
Inkscape has just recently switched from 90 to 96 dpi, so if you use 0.91 or older than that would be 90 dpi.

But if you want the image to be exported at 200 dpi for the desired 4000 px /6000 px size, you need to "scale down" the object, page
by 96/200=48%.
That would call for an 1920 px/2880 px document or object or exported area size in the svg.

The png's pixel size won't be affected whether you export a 4000 px / 6000 px sized object @ 96 dpi or a 1920 px / 2880 px sized @ 200 dpi,
nor its virtual size (in MB). Only difference is the resolution saved in the file that can indicate your printer the real word units of the image.
(The 4000 px / 6000 px image printed at 96 dpi would mean a 41,66 inch / 62,5 inch final size.)

Other than that probably inkscape is not the best tool for "resampling" a file for a smaller size.
Jpegs are used commonly because they are generally smaller. Even that its compression is lossy and can add visible noise hence lowering the quality.
A raster image editor has more option for exporting to a raster format.

Jpegs can have very little compression as well. For the "highest possible quality", they can get bigger in size than png-s.

Png compression is lossless. It can save some storage space but if you want to open an image many times for editing, you can save time if you don't compress the image on loading and exporting. My guess is that printers may work the same way and their rip can digest larger png-s better than their heavily compressed doubles.

Tiff is another format used with large raster images, however inkscape can only export to png.
I may be wrong here, didn't look up if there was such an extension for saving in various raster formats.

If you'd like to export to jpg, you can also take a look at https://github.com/giacmir/Inkscape-JPE ... -extension.
Else, you could use the command line tool pngquant to locally reduce the size of pngs.

Yet another topic on resolution.

I couldn't even count how many of these topics I've read. And I still just barely understand it. It's just a good thing I don't need to print or have something printed from Inkscape. But I do wish I could understand it better, so I can help to explain it. But, I just keep trying.

Output is to be 20 inches by 30 inches at 200dpi

I have scaled the images to be 990 x 1320, using six: 3 rows of 2

Oh I just missed that last bit.
So you want to have six embedded raster images next to eachother, that when exported will be stitched to one.
Let's see if my abacus still works before bedtime.

For the 20 inch / 30 inch image to be @ 200 dpi, set the page size to 1920 px / 2880 px and scale the embedded images to fit with that size.
3 rows 2 columns? That would call for an individual raster image scaled up to 960 px/960 px.

Scaled the images to be 990 px / 1320 px? But that doesn't fit with the proportions you just described. Something doesn't add up.
Can you share the file/screenshot?

Thanks for the explanation,

A couple of notes:

My latest attempt was at 3000x4500

I resized the images in GIMP, not Inkscape.

They aren't square. That's why 990x1320.

They have space between them. That's why the numbers don't seem to add up. Horizontally. there are two images @990 and 3000-1980 = 1020 of blank space.

Irony: I tried posting a png screenshot, but it won't upload @ 559K.

Many thanks.

Re inability to upload. You could try file sharing, such as dropbox. Or the only image host I know which accepts SVG https://imgh.us