Save Screenshot DPI setting

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Wolfgang Baer
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Save Screenshot DPI setting

Unread post by Wolfgang Baer »

Hi,
H&M's build in screenshot tool has a DPI setting in the save dialog. To try out how this affects publishing I changed the value to 150 dpi (default is 72).

But when viewing the saved file's properties it is still 72 dpi.
Does the dpi feature do something different than I assume it does?
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Tim Green
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Re: Save Screenshot DPI setting

Unread post by Tim Green »

Hi Wolfgang,

It doesn't really do anything -- it is just information in the file attributes and does not have any physical effect on the actual graphics content at all. It can be interpreted by graphics programs but almost never is nowadays. Particularly in HTML it is completely irrelevant. There the only relevant attributes are the physical dimensions of the image in pixels, and those are real physical dimensions.
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Simon Dismore
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Re: Save Screenshot DPI setting

Unread post by Simon Dismore »

Tim Green wrote:It can be interpreted by graphics programs but almost never is nowadays.
Image file resolution is used more widely than you might think. If you insert a 300x300 pixel image into MS Office it will be 105.8mm high if the image resolution is 72dpi, but 25.4mm if the resolution is 300dpi. Try it in Outlook, Word or Powerpoint. The same approach is used when you place images in Adobe InDesign and Illustrator. Likewise if you make a slideshow in Acrobat by combining multiple jpgs.

Perhaps you haven't noticed this because the H&M Screen Capture tool doesn't actually record the setting correctly, which is a (minor) bug. You have to re-save the image using an app that supports resolution, such as Photoshop.
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Martin Wynne
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Re: Save Screenshot DPI setting

Unread post by Martin Wynne »

Simon Dismore wrote:Image file resolution is used more widely than you might think. If you insert a 300x300 pixel image into MS Office it will be 105.8mm high if the image resolution is 72dpi, but 25.4mm if the resolution is 300dpi.
But these real-world sizes are meaningless if the image is viewed on a screen. Which can have any resolution setting, any physical size from a pocket device to an entire wall, and be easily zoomed in or out.

The DPI file setting is meaningless unless the image is physically printed, and then only if the scaling is set to "none" or 100%. Which isn't the usual default settings of "fit to paper" (for general documents) or "dot-for-dot" (for hi-res photo printing).

Martin.
Wolfgang Baer
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Re: Save Screenshot DPI setting

Unread post by Wolfgang Baer »

So the dpi setting would do what I assumed, if it would work correctly. As most of my questions so far are related to the printable PDF output, the dpi setting in the screenshot tool would be nice to have (rule of thumb for images that do not get upscaled is 150 dpi for standard print, 300 dpi high quality print). But this is only a tiny issue, as there are third party tools to batch convert images (might anyway be faster to batch convert a bunch of images than to set the dpi each time in the screenshot tool).

And by the way,
in case my posts sound negative (not intended), I like to say that V7 of H&M is is great. V6 already was great but 7 raised the bar even higher.
And thanks for this responsive forum.
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Alexander Halser
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Re: Save Screenshot DPI setting

Unread post by Alexander Halser »

The DPI setting of images is unused in all of the outputs of Help+Manual, including PDF and DOCX. The only thing that matters is the pixel size of the image in relation to the screen resolution (system DPI), which the editor zoom factor is the equivalent for, and the scaling size, if you resize the picture in the editor. There is always a dedicated size that the picture should be displayed at, the native resolution of the image will be scaled to this target size. Absolutely regardless of the dpi value. That's true for the editor and every output, HTML, PDF, eBooks or DOCX.
Alexander Halser
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Simon Dismore
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Re: Save Screenshot DPI setting

Unread post by Simon Dismore »

Martin Wynne wrote:these real-world sizes are meaningless if the image is viewed on a screen
As Alexander says, it doesn't make any difference if your workflow is entirely based on Help & Manual. H&M's screen capture tool always records the resolution as 72dpi, which is usually wrong but this doesn't matter because H&M's editor ignores it anyway. Indeed I rather like the way that H&M publishes the same output dimensions regardless of the screen resolution of the capture.

But that's a special case. All the capture tools I use (snipping tool, snagit, phantomjs) detect the source screen resolution, and if I put multiple bitmaps onto the same Word page (or PowerPoint slide, Outlook email, Illustrator/Inkscape SVG etc) it is immediately obvious if I've mixed different resolutions: a screenshot of a large fonts (144dpi) desktop captured by H&M will be displayed twice the size of a capture by snagit, even though they are both the same dimensions in pixels and were captured on the same system. This happens regardless of whether I intend to print the pages/slides. So it's something to be aware of, e.g. if you plan to archive your screenshots so that other designers can use them.
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Martin Wynne
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Re: Save Screenshot DPI setting

Unread post by Martin Wynne »

Simon Dismore wrote:But that's a special case. All the capture tools I use (snipping tool, snagit, phantomjs) detect the source screen resolution, and if I put multiple bitmaps onto the same Word page (or PowerPoint slide, Outlook email, Illustrator/Inkscape SVG etc) it is immediately obvious if I've mixed different resolutions
Hi Simon,

You have lost me there -- but then I don't use those programs. :? In every program where I insert images I'm invited to drag the outline to the required size. The program them StretchDraws the bitmap to fill the outline. The DPI setting in the image file is irrelevant. Here's a bit of Jing video showing an image captured with the Snipping Tool being inserted in PagePlus:

http://screencast.com/t/ijNiqV2HM

The same applies when images are used in my own software and in H&M, the user is invited to specify the container size, either directly or by dragging. The DPI setting doesn't come into it.

regards,

Martin.
Simon Dismore
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Re: Save Screenshot DPI setting

Unread post by Simon Dismore »

If you ignore the invitation to drag, and instead simply left-click the mouse, PagePlus will insert the image without re-scaling. I've just tried it with two 300x300 captures of the top left hand-corner of my desktop, taken with snagit:
PagePlus dpi-aware demo.png
The image on the left was captured with the display configured with large fonts (144dpi), and the one on the right was captured with the display configured with normal fonts (120dpi). PagePlus automatically sized the 144dpi image to 2.083 inches at 100% scale (300 pixels / 144 dpi = 2.083 inches). It automatically sized the 120dpi image to 2.5 inches at 100% scale (300 pixels / 120 dpi = 2.5 inches). A 300x300 pixel capture made by H&M would have been (300 pixels / 72 dpi) = 4.167 inches.

I checked three methods for inserting the images into PagePlus: (i) using paste, (ii) using Insert Picture | From File..., and (iii) adding the pictures to the Assets library and dragging them onto the page. The result was the same with each method. If you don't tell PagePlus to rescale the image, it calculates the on-page dimensions by scaling the image pixel dimensions according to the number of dpi in the image file. Every page layout program I've ever used has done this, which is why I was surprised by Tim's assertion. It is only in web layout programs like Dreamweaver and H&M that the dpi setting is ignored.
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Martin Wynne
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Re: Save Screenshot DPI setting

Unread post by Martin Wynne »

Simon Dismore wrote:I checked three methods for inserting the images into PagePlus: (i) using paste, (ii) using Insert Picture | From File..., and (iii) adding the pictures to the Assets library and dragging them onto the page. The result was the same with each method. If you don't tell PagePlus to rescale the image, it calculates the on-page dimensions by scaling the image pixel dimensions according to the number of dpi in the image file
Hi Simon,

That's all news to me, and I'm mighty puzzled. :?

It's not often I don't drag an outline for an image, but if I simply click, images from any source are shown at 97 dpi (my screen is 120 dpi) in my copy of PagePlus. This image was 800 wide, so PagePlus added a single border all round making it 802, and then scaled it at 97 dpi to 8.268" for printing (real-world inches are meaningless on a screen). The 97 dpi value can be changed by moving the Web <> Print slider to control the image quality (which causes it to be resampled, maintaining the size:
pp7_img.png
We seem to have strayed off Wolfgang's question. :)

Martin.
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Last edited by Martin Wynne on Thu Aug 06, 2015 4:51 pm, edited 1 time in total.
Simon Dismore
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Re: Save Screenshot DPI setting

Unread post by Simon Dismore »

Hi Martin, I think that's PagePlus rescaling the image so it will fit on an A4 page. Try using a smaller image or a larger page.

I prefer not to drag because I want to preserve the relative sizes of images. As we've discussed in the past, it is best to avoid the blurred effect of rescaling, so I like to work at 100% or 200% of the original, cropping rather than scaling. Also IMO it looks unprofessional if the same font changes size in every different screenshot!

Update: I've just been trying PagePlus and there seems to be a further issue. Running on a 120 dpi system, if I save a screenshot from the snipping tool or snagit it is recorded as being at 120 dpi, and PagePlus respects this when I insert the file, including if I copy the file in Windows Explorer and paste in PagePlus. However, when I copy directly from the snipping tool or snagit, via the clipboard and not via a file or filename, then PagePlus sees it as being 96 dpi. So this is a confounding factor.
Wolfgang Baer
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Re: Save Screenshot DPI setting

Unread post by Wolfgang Baer »

To Martin,
the topics you discuss caused my initial question. Because most graphics and dtp packages take dpi into account, I tried the dpi setting of H&M's screenshot tool. So everything totally on topic :)
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Martin Wynne
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Re: Save Screenshot DPI setting

Unread post by Martin Wynne »

Simon Dismore wrote:Update: I've just been trying PagePlus and there seems to be a further issue. Running on a 120 dpi system, if I save a screenshot from the snipping tool or snagit it is recorded as being at 120 dpi, and PagePlus respects this when I insert the file, including if I copy the file in Windows Explorer and paste in PagePlus. However, when I copy directly from the snipping tool or snagit, via the clipboard and not via a file or filename, then PagePlus sees it as being 96 dpi. So this is a confounding factor.
Hi Simon,

Thanks. I found the same when pasting directly from a capture program. If the clipboard format is CF_BITMAP, it is a pointer to a BITMAP structure which is the raster data but doesn't include any dpi info. If the clipboard format is CF_DIB, it contains the actual bitmap and a BITMAPINFO structure which does include dpi info (actually coded as pixels per metre, which explains some rounding effects -- PagePlus often shows 119 dpi instead of 120, or 97 dpi instead of 96).

regards,

Martin.
Simon Dismore
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Re: Save Screenshot DPI setting

Unread post by Simon Dismore »

Interesting. I can't get PagePlus to paste from the clipboard as 120 dpi, except by copying a file from Windows Explorer. How did you do it?
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Re: Save Screenshot DPI setting

Unread post by Simon Dismore »

Simon Dismore wrote:How did you do it?
Hi Martin, please ignore that enquiry: I've uninstalled PagePlus now.
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