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William Leue
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Joined: 03/07/2020
Location: United States
Posts: 405

Posted: 10:02pm 08 Apr 2021

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I have some puzzling behavior going on in a program I am writing, and I am hoping somebody can help.

If I do this simple thing:

Mode 1,12
Load PNG "blah.png"
line 0, 0, 799, 599,, RGB(RED)

everything works as I expect; that is, the image is shown and then the red line is drawn on top of the image. (I am using 12-bit color because I will eventually want to draw translucent stuff on top of the image.)

However, if I do this instead:

Mode 1,12
page write 1
load PNG "blah.png"
page write 0
page copy 1 to 0, B
line 0, 0, 799, 599,, RGB(RED)

The line does NOT appear on top of the image! (My actual code is more complicated but this is the essence.)

There must be something magic about the page copy but I can't imagine what it is.

-Bill

vegipete

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Joined: 29/01/2013
Location: Canada
Posts: 1127

Posted: 10:06pm 08 Apr 2021

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The line is on top of the image on page 0. However, page 1 is on top of page 0.
Edited 2021-04-09 08:06 by vegipete

Visit Vegipete's *Mite Library for cool programs.

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6264

Posted: 10:47pm 08 Apr 2021

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From my help pages (which came from Peter):

Quote The display always shows the contents of page 0 (16-bit and 8-bit) and pages 0 and 1 (12-bit). Use PAGE WRITE and PAGE COPY to avoid flashing and tearing artefacts.
For 12-bit colour depth page 0 is the lower level and page 1 the upper so the stack is: background, page 0, page 1 with each one overwriting the previous in turn as defined by the transparency values of each individual pixel.

Mode 1,12
page write 0
load PNG "blah.png"
page write 1
line 0, 0, 799, 599,, RGB(RED)
do:loop until inkey$ <> ""

Jim

VK7JH
MMedit

William Leue
Guru

Joined: 03/07/2020
Location: United States
Posts: 405

Posted: 11:28pm 08 Apr 2021

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Thanks! I always thought pages 1 and 2 were totally offscreen. That explains a lot!

-Bill

William Leue
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Joined: 03/07/2020
Location: United States
Posts: 405

Posted: 12:50am 09 Apr 2021

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It works great, once I changed which page was which. Thanks much, vegipete and TassyJim, you guys certainly deserve your Guru labels!

-Bill

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