Curious about re-sizing

[ChrisGreaves]

This is (for me) curiosity-value only.

I take a photo with my HP Photosmart R837 digital camera (a cheapie) and upload it to my hard drive.
Windows Explorer reports its size as 3,370 KB and 3072x2304 pixels.

I open the image with MSPaint and save the edited image with a new name; no edits, just Open followed by saveAs.
Windows Explorer reports its size as 657 KB and 3072x2304 pizels.

I use Windows Resizer to resize both images to "Large" (1024x768), and both saved images are cloned to 108KB and 109KB respectively. I'm prepared to treat these as equal sizes.

What is this telling me?

Does it mean that the HP camera has a terribly inefficient storage mechanism, five times (3370/657) worse than Microsoft's MSPaint?

Is there likely to be any loss in resolution in migrating from the HP native format to MSPaint?
(a.k.a. should I translate the 11,000 (14GB) of images on my hard drive, just on principle?)

[IanWilson]

This is (for me) curiosity-value only.

I take a photo with my HP Photosmart R837 digital camera (a cheapie) and upload it to my hard drive.
Windows Explorer reports its size as 3,370 KB and 3072x2304 pixels.

I open the image with MSPaint and save the edited image with a new name; no edits, just Open followed by saveAs.
Windows Explorer reports its size as 657 KB and 3072x2304 pizels.

I use Windows Resizer to resize both images to "Large" (1024x768), and both saved images are cloned to 108KB and 109KB respectively. I'm prepared to treat these as equal sizes.

What is this telling me?

Does it mean that the HP camera has a terribly inefficient storage mechanism, five times (3370/657) worse than Microsoft's MSPaint?

Is there likely to be any loss in resolution in migrating from the HP native format to MSPaint?
(a.k.a. should I translate the 11,000 (14GB) of images on my hard drive, just on principle?)

Assuming the files are JPGs, the size of the file depends not only on the dimensions of the pictures in pixels, but also the quality setting (i.e. the degree of compression) of the jpg file.

I've just experimented with a picture that was 3648x2736 pixels. Saved at a quality setting of 95, it is 1.98MB, but saved at a quality setting of only 65 it is only 494 KB.

I imagine that when you use Windows resizer to make both your photos 1024 x 768, it saves them with the same JPG quality setting so they end up the same file size despite having got there by different routes. The higher file size (less compression) pictures will ultimately be of better quality, but for some purposes (for instance putting them on a web page, you may not see a difference).

Ian

Edited to add: because of the compression you are throwing information away, so you are best to store photos in as uncompressed a state as you can. Also each time you save a JPG file you lose more information.

[HansV]

It means that MSPaint saves the .jpg with a relatively low quality factor (or high compression factor, if you prefer).
MSPaint doesn't offer you any control over the quality/compression. You may want to use a graphics utility that does, such as FastStone Image Viewer or IrfanView, both free.

[Hey Jude]

You may want to use a graphics utility that does, such as FastStone Image Viewer or IrfanView, both free.

I have been very happy with Irfanview :-)

[DaveA]

For any image that I need to resize for use in email, on a web site, in Word or PowerPoint I use the MS PowerToy Image resizer on the XP machines. BUT on the Windows 7 machines I use the free version of VSO, from http://www.vso-software.fr/products/image_resizer/" onclick="window.open(this.href);return false;, it will also work with Vista.

One can NOT see any difference between the original source and the posted version within the used application.

[ChrisGreaves]

Also each time you save a JPG file you lose more information.

Thanks Ian, but by this do you mean that a repetitive open/save of a JPG file will, over several iterations, reduce it to a fuzzy blur, rather like an oft-photocopied document?

[ChrisGreaves]

It means that MSPaint saves the .jpg with a relatively low quality factor (or high compression factor, if you prefer).

Thanks Hans. So MSPaint has a sort-of built-in resizer that arbitrarily decides to trim information in the interests of conforming to MS's low quality of images?

[IanWilson]

Also each time you save a JPG file you lose more information.

Thanks Ian, but by this do you mean that a repetitive open/save of a JPG file will, over several iterations, reduce it to a fuzzy blur, rather like an oft-photocopied document?

Yes I believe that this is the case.

Ian

[HansV]

So MSPaint has a sort-of built-in resizer that arbitrarily decides to trim information in the interests of conforming to MS's low quality of images?

Yes - MS Paint is by intention a bare-bones graphics editor that doesn't require users to take a course to use it, and to take complicated decisions. The compression factor works well for everyday usage.
People requiring more control and more advanced features have a wide range of free and commercial graphics applications at their disposal.

[IanWilson]

Also each time you save a JPG file you lose more information.

Thanks Ian, but by this do you mean that a repetitive open/save of a JPG file will, over several iterations, reduce it to a fuzzy blur, rather like an oft-photocopied document?

Further reply to this. Some information here clarifies this a bit: http://graphicssoft.about.com/od/format ... sfacts.htm

Ian

[ChrisGreaves]

Some information here clarifies this a bit: http://graphicssoft.about.com/od/format ... sfacts.htm

Thanks Ian, very interesting reading.
Especially "and it is not suitable for screen shots, "
I am in the habit of using PrtScr then pasting into MSPaint and saving as a JPEG.

[BobH]

Hello Chris,

What format does the file have when it comes off the camera? Is it possible that the image saved is a bitmap (.bmp) file that gets converted to .jpg? IIRC bitmap files are generally much larger than jpgs and as Hans and others have said, the compression ratio of jpgs is variable.

FWIW, if a jpg file has been saved with high compression, it cannot be retrieved and re-saved with lower compression. That's why this type of compression - indeed all compression that I know of - is considered "lossy" meaning that a great deal of graphic information is lost when compressed.

[IanWilson]

Some information here clarifies this a bit: http://graphicssoft.about.com/od/format ... sfacts.htm

Thanks Ian, very interesting reading.
Especially "and it is not suitable for screen shots, "
I am in the habit of using PrtScr then pasting into MSPaint and saving as a JPEG.

I've just found another page here http://www.labnol.org/software/tutorial ... ages/3917/ comparing file formats for screenshots.

Ian

[IanWilson]

Some information here clarifies this a bit: http://graphicssoft.about.com/od/format ... sfacts.htm

Thanks Ian, very interesting reading.
Especially "and it is not suitable for screen shots, "
I am in the habit of using PrtScr then pasting into MSPaint and saving as a JPEG.

I've just found another page here http://www.labnol.org/software/tutorial ... ages/3917/ comparing file formats for screenshots.

Ian

And here is the same screenshot saved in two different formats. First .jpg

screenshot test 2.jpg

and then .png.

screenshot test 2.png

I think the .png is much better in the solid colours, and the file size is smaller too.

Ian

[HansV]

I've just found another page here http://www.labnol.org/software/tutorial ... ages/3917/ comparing file formats for screenshots.

Their recommendations are pretty much what I do: .png format forscreenshots consisting of text and simple graphics, .jpg for photographs.

[ChrisGreaves]

What format does the file have when it comes off the camera? Is it possible that the image saved is a bitmap (.bmp) file that gets converted to .jpg? IIRC bitmap files are generally much larger than jpgs

Hi Bob.
The images on the camera card are JPG, and I can transfer them to the computer by a direct file-to-file transfer (e.g. drag through Windows Explorer, FileCopy in VBA etc.) and use them 'as-is". The images load correctly into any graphics program I use here.
I agree that BMPs are huge, and that's why I generally save my PrtScr snapshots as JPGs rather than as BMPs.

[ChrisGreaves]

I've just found another page here http://www.labnol.org/software/tutorial ... ages/3917/

Ian, thanks for this. I'll switch to PNG for a while and see how it goes.

I think the .png is much better in the solid colours, and the file size is smaller too.

It must be my 4 a.m. eyes, but I can't see any difference.
I see the file size difference, but that difference (16K/18K) pales when compared to a BMP version.

I just took a PrtScr snapshot and saved it into 3 separate instances of MSPaint, then saved each as BMP/JPG/PNG yileding sizes of 3,841/189/132 KB respectively.

For size considerations, either JPG or PNG is a clear winner (in this one test), but unless there is noticeable difference in quality, perhaps "compatibility" comes into it, and then we are into personal beliefs along the lines of 'Where do *I* think my image will be viewed".

In the end I'm very grateful for the links to the articles. I'd seen and accepted PNG before but always thought that JPEG was *THE* standard format nowadays.

[IanWilson]

It must be my 4 a.m. eyes, but I can't see any difference.

I think that you can see a bit of a mottled effect in the blue of the title bar on the JPG (look closely above the word Pictures, for instance). The effect is more pronounced with larger solid areas and with a lower quality factor (this was a quality factor of 85 if I remember right).

Ian

[StuartR]

I think that you can see a bit of a mottled effect in the blue of the title bar on the JPG...

I think you can also see better text in the png file, look closely at the edges of the characters in the title bar.

[ChrisGreaves]

... title bar on the JPG (look closely above the word Pictures, for instance).

OK, Ian. Thanks. Now I see it.
(I went to 800x600 on my monitor, possibly not the smartest thing to do).
I can see what you call mottled - an appropriate term according to my "oxford". I would have called it "granular", which is not as good as mottled.