Actual Size & Bitmap Image Scaling Problems

[MSotero]

While I noticed the following two circumstances in 8.1 (maybe it existed sooner) they are still present in 9.0.

First:
Once upon a time if I choose "Actual Size" then I could put my scale up to the screen or hold a scaled image next to it and see a correct relationship. But at present, actual size seems to have nothing to do with a properly scaled image. Could it have something to do with the transition from a glass monitor to a LCD? Is there a way to make actual size do what it says, actually be actual size? I might add here that this incorrect scale of the monitor display is for everything - vector or otherwise.

Second:
It is not uncommon for me to do loose hand sketches over archicad generated base drawings for presentations, scan them, and then plot them from on a normal title sheet (at times mixed with vector drawings).

However, if I merge scans into archicad (and yes I make sure the screen window view is 100% - not even sure if that matters anymore) or import them into plotmaker the image may or may not be scaled properly depending on what I did in Photoshop.

What I've noticed is that the scale is NOT correct if I had changed the Canvas size in Photoshop. I regularly do this because my scanner bed is only so big and I need to piece together multiple scans to complete some images. At present, I'm forced to place the image in either program and resize it. So far I've found the fastest way is to look at the image size (inches measurement) in Photoshop and then make the placed images match that in AC or PM which of course then changes the resolution of the placed image.

Is there reason for what is happening? A work around? Is this a bug?

Just yesterday, in a rush to a meeting I realized during the presentation that I forgot to resize a couple images and had to explain to the client that some images were not to scale. Not a confidence builder.

[Anonymous]

I would always be VERY WARY of any computer program telling me that something on the screen was 'actual size'. I would want to know that the program;
a) knew the physical width/height of my monitor
b) knew the pixel count I was using
c) knew about any distortion over the face of the monitor

When we use scanned / photoshopped images we ALWAYS include a pair (one in each axis direction) of 'reference lines' - preferably as long as possible. This allows you to rescale the bitmap/whatever within Archicad accurately. (note that many scanners elongate images by up to 2% so the X-scale may be different to the Y-scale, hence the two reference lines)

HTH - Stuart

[MSotero]

StuartJames wrote:
(note that many scanners elongate images by up to 2% so the X-scale may be different to the Y-scale, hence the two reference lines)

HTH - Stuart

Thanks Stuart, I appreciate the cautions.
Apparently those things don't seem to address what I'm experiencing though. And maybe my scanner is pretty accurate because I can lay my sketches over my plots and they always match (if I rescaled them when needed per my original post).

But as I mentioned, the screen display of Actual Size is, well, not actual size and the incorrect scale of placed bitmap images only occurs for images for which I needed to change canvas size in Photoshop. I really don't get it.

[Dwight]

most programs assume 72 dpi as being 100% and that is way off considering most LCD panels are 100dpi [ie: for actual size make it 141%]

importing scans into ArchiCAD is tricky - most reliably use the figure import tool rather than just pasting it in.....

[MSotero]

Dwight wrote:
most programs assume 72 dpi as being 100% and that is way off considering most LCD panels are 100dpi [ie: for actual size make it 141%]

importing scans into ArchiCAD is tricky - most reliably use the figure import tool rather than just pasting it in.....

Thanks Dwight.
I tried a 141% zoom and sure enough things do scale on the display properly at that magnification. So it appears that menu selection of "Actual Size" needs to be fixed as it apparently only works on 72dpi monitors.
Regarding the importing of raster images....I'd still like to find the answer as it creates a lot of extra work.

[Anonymous]

MSotero wrote:

Dwight wrote:
importing scans into ArchiCAD is tricky - most reliably use the figure import tool rather than just pasting it in.....

Regarding the importing of raster images....I'd still like to find the answer as it creates a lot of extra work.

Michael,

Dwight's suggestion is not really a lot of work and it will have the result you desire. Or you can just paste the image in directly from Photoshop and use the resize command as described in this thread: http://archicad-talk.graphisoft.com/viewtopic.php?t=5101

Very quick and it works!

Still, be aware of Stuart's caveat:

Stuart wrote:
(note that many scanners elongate images by up to 2% so the X-scale may be different to the Y-scale, hence the two reference lines)

Of course, you can use the Resize command on the X axis and Y axis separately. I would resize the entire scan, the check measurements on both the X and Y axis, then resize any error along either one.

Woody

[Anonymous]

Stuart wrote:
note that many scanners elongate images by up to 2% so the X-scale may be different to the Y-scale, hence the two reference lines)

MSotero wrote:
... maybe my scanner is pretty accurate because I can lay my sketches over my plots and they always match (if I rescaled them when needed per my original post).

The other guys have commented on 'Actual Size'. As for 'correct world size' a _lot_ of investigation has suggested the following 'guidelines' for use in our office;
a) most devices (printers, faxes, scanners) are 'very good' across the sheet. Normally negligible error.
b) Flat-bed scanners often have 1-2% elongation
c) Printers often have 1/2 - 1% elongation
d) Faxes show up to 3% elongation

... if both your printer & your scanner have the same error this might account for it? A good test might be to scan a circle both 'horizontally' and then 'vertically' and check to see the overlay. Hopefully you won't be surprised!

- Stuart

PS. From the above, it is obvious that it wasn't women who designed these devices 🙂

[Steve Jepson]

MSotero wrote:
...is there a way to make actual size do what it says, actually be actual size?

You probably already know how to do this.
Import your image with the figure tool or paste it into ArhchiCAD. Draw a line of some known length of something in the image. ( the edge of a door way or someting you know the size of), use the stretch tool to stretch the image fit the line.

[Dwight]

Using stretch has problems since figure images aren't perfectly displayed at all screen zooms. The other problem is accuracy since stretching to hit non-hotspot locations [within the figure, for instance] isn't accurate. This will show up when you zoom in closer than the zoom where you actually stretched the element.

Far better to establish the actual size of the rectangular figure and assert it in the figure dialog box. And fewer steps, too.

[Steve Jepson]

Dwight wrote:
Using stretch has problems since figure images aren't perfectly displayed at all screen zooms. The other problem is accuracy since stretching to hit non-hotspot locations [within the figure, for instance] isn't accurate. This will show up when you zoom in closer than the zoom where you actually stretched the element.

Far better to establish the actual size of the rectangular figure and assert it in the figure dialog box. And fewer steps, too.

"Far better"? "Fewer steps"? I am sceptical. I can't.

Draw line-- Stretch image- is only two steps and it eliminates a lot of useless math.

I am assuming that there is no means what ever by which an image can be imported into ArchiCAD that is accurate enough for anything other than a visual aid. Perhaps this is not true.

The objective of my method is to make the scale of the objects in the image as accurate as possible rather than trying to make the entire image exactly the same size as the original image which may not help at all.

I have a laser devise I can use with my camera that will measure the distance from the camera to the objects in the picture and other rerference points very accurately. Using a little math, I can import images "to scale", however, the objects in the image can be made more "to scale" by stretching the image to match a line of a known length than by any other means I have tried.

I contend that the method I have suggested is the "Far Better" and requires "Fewer steps".

Try this...import, or copy and paste a floor plan image from one of those house plan sites on the web into ArchiCAD. Now that the image is in ArchiCAD, what is the best way to make it into a 1/4" "to scale" image? Draw a line 3' long and stretch the image so the 3' front door matches the line or try to tweak the overall size of the image?

"Graphically" to scale is all you can ever get an image to be. This being the case a graphical means of resizing the image is a method that works just as well as any other, if not better.