Author Topic: Working with large bitmaps  (Read 164 times)

Shipmodeler

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Working with large bitmaps
« on: August 31, 2017, 02:36:29 PM »
I'm using a scanned drawing to trace over.  It's a big drawing I had scanned and I loaded it into DC3Dv23.  I converted the scan to the smallest file possible in Photoshop before loading it into DC.  Unfortunately, the drawing is so big data wise, drawing takes forever.  What takes less than a second for screen regeneration is taking 1 to 2 minutes and longer.  I can't continue at this pace.  Does anyone know a technique so I can use the scan as an underlay that doesn't take forever to make drawings?

Any help would be appreciated.

Shipmodeler
"A man can never say he has truly lived until he has built a model ship"
Ronald Reagan

minstrel

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Re: Working with large bitmaps
« Reply #1 on: September 01, 2017, 04:36:09 AM »
Perhaps saving at 72dpi will help [300dpi unnecessary and creates gigantic file sizes].

Rob S

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Re: Working with large bitmaps
« Reply #2 on: September 01, 2017, 07:23:40 AM »
Have you got a colored image, or black and white?  File size for BW can be much smaller as well.

How big is the image in pixel size and filesize, and how big is the drawing file with the image removed?

Is the image a jpg or some other format?

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DrollTroll

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Re: Working with large bitmaps
« Reply #3 on: September 01, 2017, 07:35:04 AM »
Unfortunately, the file size is no real indicator of how much space it will take in memory once displayed on the screen. Regardless of the color format of the original file, I believe DesignCAD reads it into memory as a color image at 32 bits/pixel (maybe 16 bpp if that's your screen color setup). So it's basically down to how many pixels in the image.
25 years with DesignCAD

Rob S

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Re: Working with large bitmaps
« Reply #4 on: September 01, 2017, 08:11:02 AM »
There goes most of my thoughts down the drain....

Is it possible to divide the image into say 4 parts and trace those parts of the drawing at a time, and thus only have that part of the image loaded?

I'm not sure what the effect on drawing speed would be if the other parts of the image are loaded on separate layers but their layer is turned off??

Have you tried both red mode and standard mode?
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Shipmodeler

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Re: Working with large bitmaps
« Reply #5 on: September 01, 2017, 10:51:40 AM »
I think I figured out how to make this work.  After saving the file as small as possible, I cropped the drawing photo, creating a smaller (thanks, Rob S) drawing to trace.  Realistically, since there are a number of drawings on the sheet, it would be best to work on it that way to keep everything a consistent scale, but that isn't practical given the long screen regeneration times.

I was hoping someone here knew a trick or a command I wasn't aware of to simplify everything.  Thanks anyway.

Shipmodeler
"A man can never say he has truly lived until he has built a model ship"
Ronald Reagan

JJG

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Re: Working with large bitmaps
« Reply #6 on: September 01, 2017, 01:41:32 PM »
Shipmodeler,
a trick is to use png-image (or sometimes bmp) instead of jpg or other tif and whatever.
this way is Designcad more efficient with.
 ;)

Shipmodeler

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Re: Working with large bitmaps
« Reply #7 on: September 01, 2017, 02:41:58 PM »
Screen regeneration is working well since I rebuilt the trace drawing.  I went to photoshop and cropped the individual drawings, then pasted them separately into the new drawing on separate layers.  I can now deactivate the drawings I don't need for reference and draw as usual.  With all the layers visible, it looks like one large drawing, which is what I wanted.

Thanks to all for the suggestions.

Shipmodeler
"A man can never say he has truly lived until he has built a model ship"
Ronald Reagan

Rob S

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Re: Working with large bitmaps
« Reply #8 on: September 01, 2017, 03:41:54 PM »
The Designcad forum strikes again!!!

Very glad that worked for you
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Dr PR

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Re: Working with large bitmaps
« Reply #9 on: September 01, 2017, 04:51:31 PM »
Shipmodeler,

Here are a few thoughts.

1. Convert the drawing to bitmap in Photoshop. I often use 150 dpi for large drawings where I don't need to read the small print.

I have some 3' x 12' drawings scanned at 9600 dpi - about a gigabyte -  and reducing them to 150 dpi bitmaps greatly reduces file size.

DesignCAD may convert them to RGB color and enlarge them, but the smaller file sizes greatly reduce file loading times.

2. If you are cutting a larger file into smaller parts BE CAREFUL! DesignCAD does not always imports bitmaps at the same resolution (scale). If you import a bitmap image, zoom in, and import it again the resulting bitmaps will not display the same size!

It seems the program maps image pixels to display pixels, and not referenced to anything in the drawing (not even the drawing units), so the bitmap will be imported at a size that matches bitmap pixels to screen pixels. If you change the zoom level the next image will again be mapped to the screen pixels. And when you change the zoom level the previously imported image will be a different image size on the screen, so the pixel density of successively imported images will be different in the DesignCAD drawing.

In other words, each bitmap is imported at a scale entirely independent of earlier bitmap imports.

****

Here is how to import multiple bit maps at the same pixel density so that multiple segments of the same image will appear at the same scale in DesignCAD:

1. Before importing any bitmaps, select an empty layer and draw a horizontal line of any length. This is the reference layer. Lock it so it cannot be changed. Put nothing else on this layer.

2. While in the reference layer with all other layers disabled use "View/Fit to Window" (CTRL W) to zoom the screen so the reference line spans the entire main window. This sets the screen pixel density relative to the reference line.

3. Go to an empty layer you want the bitmap image on - DO NOT CHANGE THE ZOOM LEVEL!

4. Import the bitmap image.

5. To import another bitmap image go to the reference layer and disable all other layers. Then go to step 2.

6. Continue until you have imported all bitmaps.

7. Keep the reference layer and line until the drawing is definitely finished and you no longer need to import another bitmap. Or just keep the reference forever.
 
I have done this many times to match several scans of a large drawing so I can trace them. I have found no other way to ensure that all scanned images come in at the same scale.

Phil
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Shipmodeler

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Re: Working with large bitmaps
« Reply #10 on: September 01, 2017, 08:13:50 PM »
"DesignCAD does not always imports bitmaps at the same resolution (scale)."

Yeah, I noticed that.  Thanks much for the scaling technique.  I have printed that out and included it in my DC3D reference folder for future use.  Fortunately, I drew a scale on the plans before I had them scanned so I could use it for reference on all the drawings when I resized them on the tracing sheet. 

Thanks again.

Rusty
"A man can never say he has truly lived until he has built a model ship"
Ronald Reagan

bdeck

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Re: Working with large bitmaps
« Reply #11 on: September 03, 2017, 04:28:42 PM »
If you can get Photoshop to break the image into, say 4 equal sized tiles, you may not need the registration marks.

With or without registration marks, here is a macro from an old thread that may help position and rescale the tiles in DC:

http://forum.designcadcommunity.com/index.php?topic=3044.msg16346#msg16346

bd




Shipmodeler

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Re: Working with large bitmaps
« Reply #12 on: September 03, 2017, 07:09:18 PM »
Dr. PR had it.  All the images were drawn on the same page in the same scale.

Shipmodeler
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Ronald Reagan

Lar

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Re: Working with large bitmaps
« Reply #13 on: September 05, 2017, 11:47:03 AM »
What I do when having to load multiple bitmaps is:

If the bitmaps are the same size:
Load one and resize as necessary using 2 selection handles and the move command. Then turn on 'select when created' and load the other bitmaps (one at a time) by snapping to 2 opposite corners of the first image and move to final location.

If bitmaps are different sizes but same dpi:
I load them one after the other without changing the zoom. When all are in I select them all, set 2 handles on one, resize them all using the move command then locate them one at a time where necessary.

If they are different sizes and different dpi then I bite the bullet and load and resize one at a time.


Lar
« Last Edit: September 05, 2017, 11:48:54 AM by Lar »