Hi all,
First of all, the basics--I am using PDFCreator v1.7.2 on Windows 8.1 64-bit. Now to the story. I was noticing some weirdness regarding file sizes when printing out some Powerpoint slides into PDF format, and that made me do some systematic testing. The results indicate some unexpected behavior--that PDFCreator seems to respect the bitmap downsampling dpi setting for a range of values, but that relationship breaks down at a certain dpi (and apparently any higher dpi value).
More specifics--I have a 1024x645 pixel color bitmap in Powerpoint, and it is set to print out about ~6.9" wide in a form. Let's round that to 7" just to keep numbers simple. So when I change the PDFCreator dpi setting to 50 dpi, I am expecting the resulting bitmap to be downsampled to ~350 pixels wide (i.e. 7" x 50 dpi). And indeed, that occurs--in the outputted PDF, the bitmap is ~350 pixels wide. So I set it to 60 dpi, do the same thing, and expect the resulting bitmap to be about 420 pixels wide (i.e. 7" x 60 dpi). Woo-hoo, it ends up that way. I continue forward so on and so forth, and all the way up to the 98 dpi setting, everything is great. But when I get to 99 dpi and greater, PDFCreator seems to lose its brains, and no longer respects the dpi setting value. It just spits out the full resolution bitmap, but at 1023x645 pixels in size (note that the width is one pixel shorter than the original 1024 pixel wide bitmap).
Here are the actual numbers that I gathered while progressively incrementing the dpi setting from 50 dpi up to 130 dpi. When I recognized the problem zone was between 90-100 dpi, I methodically changed the dpi setting by increments of 1.
So anyway, that's the story of what I am seeing--PDFCreator seems to downsample appropriately from 50 dpi all the way up to 98 dpi, but once it hits 99 dpi or higher, the program seems to lose track, and just spits out the fill resolution bitmap. Has anybody noted a similar problem?
Many thanks in advance for your help and comments!
verbage
I had a 3-column table of values that pasted in beautifully, and it looked great, but it got vaped during posting. So here’s a plain text version below.
DPI setting Width in pixels Height in pixels
50 341 215
60 415 262
70 485 305
80 554 349
90 623 393
91 630 397
92 637 401
93 644 406
94 651 410
95 658 415
96 665 419
97 672 423
98 679 428
99 1023 645
100 1023 645
110 1023 645
120 1023 645
130 1023 645
verbage
Hi,
thank you for investigating this issue, we will have a look at this.
But it can’t “upsample”, so you can’t increase the DPI over the original image.
regards,
Robin
Hi Robin,
Thanks so much for your response, and for looking into this. Regarding upsampling, I am definitely not trying to do that–I only want PDFCreator to downsample according to the dpi settings.
Regarding the original image, it is 1024 pixels wide, and on the page it has a physical output width of ~6.9". So when PDFCreator is set to 100 dpi downsampling, I am expecting it to produce a downsampled bitmap that is 690 pixels wide (i.e. 6.9" x 100 dpi). In fact, it follows this basic logic from between 50 and 98 dpi. But as soon as I get to 99 dpi, the logic falls apart, and the bitmap is included at its full, raw resolution, i.e. it is not downsampled.
To take this further, given a 6.9" output size, and a 1024 pixel width of the original image, the break point between downsampling and doing nothing should be about 148 dpi (i.e. 1024 pixels / 6.9"). However, as you can see from the table above, PDFCreator starts doing nothing (i.e. no downsampling) at much lower dpi settings. But from 99 up to 130 dpi (where I stopped testing), there is no apparent difference in output. This is clearly still within the range of when downsampling should be happening, but it is not.
For certain, the results from the above are only coming from one program–Microsoft Powerpoint. I have not tested with other programs–I only noticed it because of the weirdness with files sizes that I mentioned in my original post. Anyway, thanks again for looking into this, and I’ll be happy to do more testing if need be.
verbage
Hi,
if you like you could try the beta to our completely rewritten PDFCreator, I wont be able to look at this untill some time next week. Here is a link:
http://download.pdfforge.org/download/pdfcreator/1.9.2-beta/PDFCreator-1_9_2-setup-beta.exe?file=AMIfv964-EjxmXDOGU4RtqU7xHtAWQu_BO1e3dHCZJuyF2-gzppGAd0RrfRClB4BMEiHXgGcKj2AYdBTmIWt9-hwVmsUwYXcJseyP2akXzmVRxyX_9f96jz7PdxGoTsIdbqQkOElZicK0B6t645V7RnuFrTriLaQbRvrJO7ZltVw0kBBzU4hI5w
regards,
Robin
Hi,