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learning the ropes... picture size

Posted: Tue Mar 19, 2019 5:22 pm
by tjensen
Hi all.
I'm just learning things here and have stumbled across my first head scratcher... I make save a tiff file from Photoshop at 300 dpi and 3 inches. When I open it in PEP6, it shows the correct pixel count, but the resolution is 100 dpi and the image size is now 3 times larger.
Question: Why? Is it possible to change the 100 dpi setting in PEP6? Will I have to just automatically downsize all images before importing them?
Sorry if this is a stupid question.
Cheers
Tim

Re: learning the ropes... picture size

Posted: Tue Mar 19, 2019 9:08 pm
by Picengraver
You can resize your images in PEP. Click on the Edit button. You will need to set the pixel resolution (the distance from pixel to pixel) to the size you want your pixels to be (for lasers that is normally 0.006 inches to 0.007 inches), then set the size you want the final image to be. Save the image and reload it into PEP to set up your engraving. This is covered in the Tutorial.

Re: learning the ropes... picture size

Posted: Wed Mar 20, 2019 7:50 am
by tjensen
Sorry, I meant the default picture dpi settings so that I don't have to resize each image.

Why doesn't it default to the specs of the image?

Re: learning the ropes... picture size

Posted: Wed Mar 20, 2019 12:21 pm
by Picengraver
Because for one thing engraving with a bit or a laser diode at 300 DPI (0.003333333" - 1"/300) is not feasible or physically possible. So I set 0.01" as the default. And I think you will also run across other images at 96 DPI and 72 DPI, depending on source.

For engraving, images have to be resized to suit the chosen pixel to pixel distance.

Re: learning the ropes... picture size

Posted: Fri Mar 22, 2019 6:28 pm
by tjensen
Just tried to produce a gcode from a grey scale test image. When I ran it through LaserGRBL, the laser turned on low power, but didn't burn anything. When I examined the code, there were no S commands to change the laser strength. I guess I don't understand the coding process, I thought greyscale pixel intensities were translated to voltages. Doesn't that mean there should be S commands of different values in the generated code?

Re: learning the ropes... picture size

Posted: Fri Mar 22, 2019 7:12 pm
by Picengraver
Yes, S commands are needed. Sounds like a settings issue. Can you post a screen shot of your PEP settings?

Re: learning the ropes... picture size

Posted: Fri Mar 22, 2019 9:04 pm
by tjensen
Umm... apparently not... can't figure out how.

Generated the code using the analog\PWM setting if that helps at all...

Re: learning the ropes... picture size

Posted: Fri Mar 22, 2019 9:32 pm
by Picengraver
OK, can you post the first 25 lines of your gcode file?
To attach a file, click on the Full Editor and Preview button.

Re: learning the ropes... picture size

Posted: Fri Mar 22, 2019 10:10 pm
by Picengraver
Tim,
See the setting on page 4 of the tutorial as a guide for setting up PEP. Set the Pixel Resolution to 0.006" / 0.1525mm to start instead of the 0.01" shown. This should get you started, but some experimentation/tweaking with setting will be needed to suit your specific setup.

Re: learning the ropes... picture size

Posted: Sat Mar 23, 2019 7:23 am
by tjensen
Here is the screenshot of the setup I tried along with some of the code. I used the settings on p14 of the manual.
Thanks again.
screenshot.jpg
screenshot.jpg (169.76 KiB) Viewed 2366 times

G64
G20
F100
G01 Z0
F100
G01 X0 Y0 Z0 F100
M03
X-0.01 Y0 Z0 F100
X-0.01 Y0
X0 Y0 Z-0.0015 F98.5
X0.01 Y0 Z-0.0015 F98.5
X0.02 Y0 Z-0.0015 F98.5
X0.03 Y0 Z-0.0015 F98.5
X0.04 Y0 Z-0.0015 F98.5
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X0.1 Y0 Z-0.0015 F98.5
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X0.2 Y0 Z-0.0015 F98.5
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X0.49 Y0 Z-0.0015 F98.5
X0.5 Y0 Z-0.0015 F98.5