Problem creating a pdf of an upscaled image

[krs]

Hi - I'm a bit baffled....maybe someone can help

I have a jpg image that shows as 509x660 pixels at 200 pixels/inch resolution in Preview
If I convert that toa pdf using Preview (or Acrobat) I end up with the same size as the original jpg - OK that's expecte.

I then used Preview to upscale the image to say 800 pixels horizontally with both resampling and proportional checked in the preview tools setting.
New image is larger as expected an text more readable - however, and this is the problem:
The pdf image created from the larger, resized image is no different than the pdf from the original small image.
I used both Preview and Acrobat to convert from jpg to pdf - same result.
How do I create a pdf from the upscaled larger jpg that is the same size as that jpg?

PS: Running Mojave on a 2012 Mini

 

[IWT]

Hi krs

I did what you did but in reverse order you might say. Exported a photo from Photos app. Created a duplicate of it.

Then I used Preview to increase the pixels in the duplicate which created a much larger image. The original was 749 kb and the upscaled image = 1.4 MB

Then I created a PDF of both the original (753 kb) and the upscaled image (1.4MB).

In other words, I did the upscaling before the PDFs. Am I right in interpreting your actions as creating the PDF first then upscaling?

At any rate, using my method, I achieved a PDF of the upscaled picture which was the same size as the PDF of the original, but at a much higher resolution.

Gosh: I hope this helps and that my explanation and conclusions were understandable!!

Ian

 

[krs]

At any rate, using my method, I achieved a PDF of the upscaled picture which was the same size as the PDF of the original, but at a much higher resolution.

Thanks for trying, Ian

I had done this the same way as you - increased the jpg image in preview first using tools>Adjust size and changing the pixel width leaving the resolution the way it was.
That gave me a larger image on the monitor.
But when I then made a pdf of that upscaled jpg image, the size of the pdf (as it shows on the screen) comes out as the same size as the jpg before I upscaled which seems to be identical what you are seeing (bolded in your comment).
I set the View option for the jpg and pdf at "Actual size" and the pdf is much smaller than the jpg it was created from.
The file size of the pdf is much larger but that doesn't help me - I need to make the size if the image on the screen bigger when converted to a pdf.

PS: I think I had this issue years ago but can't remember how I solved this.

 

[IWT]

Really sorry I wasn't able to help. If you recall the solution, do let us know.

Ian

 

[krs]

I tried a few more things - posted just for reference:
1. Changed image format from jpg to png and converted png to pdf - same problem
2. Changed image format from jpg to tiff and converted tiff to pdf - same problem
3. Took a screen shot of upscaled image using 'Grab', that generates a tiff image by default. Converted that to pdf, doing that worked (I actually expected that), but it doesn't help either in the end with the image because now the resolution is only the resolution of my monitor which is 72 pixel/inch.
But maybe it provies a hint what to do.....