Convert Jpeg to 300 dpi

Open the file in Preview. Then Tools - Adjust size.

My instructions were for printing out purposes.

A jpeg image off of the web cannot be scaled up and printed out to a similarly sized digital camera image, as the digital camera image WILL HAVE MANY, MANY more pixels in it than those types of jpeg images that are found in typical websites.

As I stated in my reply, you NEED ( I don"t give a flyin" crop about the difference in PPI vs DPI as Photoshop uses DPI for resampling purposes) to increase the amount of pixels in web images if you are planning to print out images on media to the same pixel amount/density found in typical digital images taken from today's high megapixel digital cameras to achieve a similar print quality and look.

I know what I am talking about, folks!

I am a 20 year veteran Photoshop and Painter user who has been creating printed artworks in these applications for very many years!

I mentioned, a couple of times, references to needed pixel quantity for printing out of web based jpeg images, which contain low pixel amounts that need to be increased for acceptable printed image quality.

Let us NOT start a debate about this. I was pretty clear about what has to be done. All of it in reference to printing out a final image.

These are but two approaches that need to be done to bring up the pixel count of low pixel images that can later be printed out.

I assumed that is why the OP was asking how to convert the images to 300 DPI because the OP wants to, eventually, print out these images.

For the digital camera images, you can do what rkaufmann suggests.

For images off of the internet, the process is much more complex and involved.

You need some sort of more comprehensive image editor that will tell you the physical size of the image, the file size in MBs and the actual DPI.

Then, you will need to do something called image resampling or image interpolation to slowly increase the images' resolution to get those low resolution web images up to the 300 DPI resolution.

Just changing the DPI of a low res web image to 300 DPI does NOT make it a high resolution DPI image, suitable for printing.

All that does is take the limited pixels in those low res jpeg web images and makes them bigger (instead of adding more pixels to the image) making the image extremely blurry and digitally pixelated.

There are more than one way to get extra pixels into these low res web images.

The easiest and most direct way is too have an image editor capable of resampling images and reasmple the image up/larger by DPI increments of 25 DPI increments until you reach the 300 DPI image. This means resampling the image larger in 25 DPI increment around 10-12 times to reach the actual 300 DPI pixel resolution.

Another method if the image editor you choose has Layers capabilty is to make/copy the original image into 3-4 layer copies, then flatten or reduce those 3-4 Layers down to just one layer. Then, go ahead an proceed to follow the previous instructions above.

These procedures will keep those low res jpeg web images as sharp as is possible using these procedures and will cause minimal blurring and pixelation ofbthe image and allow you to slightly increase the physical size of these new higher res images if needed. I would not increase the physical size of the newly resampled images by any more than 10-15%.

Good Luck!

If you plan to print out all of these images, my advice and procedures for resampling web based jpeg images stands.

This is what you MUST do to get the pixel density/amount of pixels to increase to get web based jpeg images up to the same pixel amount/resolution quality/levels of images taken from a digital camera to be printed out.

The image quality of web based jpeg images will be drastically different if you do not follow my outlined advice.

😉

the number of pixels is the important variable here, i guess everyone agrees on this, and Old Toad's suggestion is very appropriate on this delicate subject of DPI

See also, in Ken W Watson's "All about digital photos",

"What print shops really want " at

http://www.rideau-info.com/photos/printshop.html

How do I convert photos to 300 DPI?

DPI is meaningless until you select a print size. More about that at The Myth of DPI

Are theses images from a digital camera or images from a website?

Your welcome.