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Old 15 March 2020, 01:17   #1
Sivee
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Noob question re fixing stretched images

Hi,
I am trying to take an image in jpeg format off my PC and convert it to an IFF file as a desktop background image on the Amiga. I processed the image on the PC first so that it was 640 x 256 in dimension using Paint.net and then loaded it into Ultimate Paint. The reason for that being that Ultimate Paint can save to IFF format. I have found if I use the "Adaptive w /palette" option and set the colours to 256 it looks colour wise and quality wise on the Amiga as pretty much the same as the original JPG. However, when I load the image to the background on the Amiga it looks stretched in the vertical direction.


Here are the two images shown side by side on my website (sivill.com):


Images side by side


Is there a way I can manipulate the image so that when displayed on the Amiga (or WinUAE) that it looks correctly proportioned?


Graham Sivill
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Old 15 March 2020, 01:46   #2
DamienD
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Hey there Sivee,

Welcome to EAB

Try creating / converting the image at 320 x 256 and see how that goes

Though depending on your original image; you may need to add "blank" areas to keep the resolution / aspect ratio on the Amiga.
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Old 15 March 2020, 02:09   #3
Sivee
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DamienD,

I will give that a try!

Graham Sivill
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Old 15 March 2020, 03:08   #4
Sivee
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Ok this is how it looks now:

https://sivill.com/?page_id=863

So it looks a better proportion but the Scalos Pattern is set to "Fit Size" yet it still insists on tiling it?

Graham Sivill
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Old 15 March 2020, 13:22   #5
amiwolf
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Remember, on a 640x256 screen the pixels are double height. When you scale the image, you must unlock the aspect ratio.

Example IFF* attached:

*Marked as 68k because this forum won't accept an iff extension.
Attached Files
File Type: 68k Ferrari Enzo 256.68k (49.7 KB, 11 views)
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Old 15 March 2020, 15:28   #6
TroyWilkins
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Would it be worth trying loading it up in PPaint on the Amiga (or on WinUAE) and then changing the resolution that way and saving it as an IFF from there? That way it should retain the correct aspect ratio.
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Old 16 March 2020, 11:02   #7
Sivee
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@amiwolf,

Yes, that image looks exactly as I wanted it to. Can you explain how you did that. I understand how in a graphics program you can untick the "maintain aspect ratio" box and adjust the width and height separately, but what width and height did you choose?

Siv
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Old 16 March 2020, 12:33   #8
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Quote:
Originally Posted by Sivee View Post
@amiwolf,

Yes, that image looks exactly as I wanted it to. Can you explain how you did that. I understand how in a graphics program you can untick the "maintain aspect ratio" box and adjust the width and height separately, but what width and height did you choose?

Siv
640x256! It was a quick and dirty job that didn't account for Amiga's 5:4 display. Doing it properly, first crop your 1024x768 4:3 image to 960x768 (5:4) and then scale it to 640x256 with "maintain aspect ratio" unticked to create a squished image (Attached thumbnail). This will be stretched back into the correct look by the the non-square pixels on a 640x256 screen.
Attached Thumbnails
Click image for larger version

Name:	Ferrari Enzo squished.jpg
Views:	15
Size:	68.0 KB
ID:	66479  
Attached Files
File Type: 68k Ferrari Enzo 5-4.68k (49.2 KB, 2 views)
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Old 16 March 2020, 12:59   #9
Sivee
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@amiwolf,
Thanks, I figured it out from your original email and managed to do it myself before I got your latest reply.
See my F40 image:

https://sivill.com/?page_id=863

Last edited by Sivee; 16 March 2020 at 13:10.
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Old 16 March 2020, 21:34   #10
Sivee
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@TroyWilkins,

Thanks for your reply, sorry I missed yours as I went off following amiwolf's method.
I did try opening the image in PPaint but for some strange reason I kept getting out of memory errors so I gave up on it.

The method I now use is to get my picture to the correct dimensions first in Paint.net on the PC ie 960 x 768, usually this means shrinking the image to as close to 960 x 768 whilst maintaining its aspect ratio as most images are huge, then when I have it close then crop out a 968 x 768 section that contains the image I want on the Amiga. Once I have that sorted then I resize the canvas (as it's called in Paint.Net) to 640 x 256 which makes is look squished in the vertical direction on the PC.

I then load the resultant image into Ultimate Paint where I save it as IFF format. I have found in that application if you select the "Adaptive w/ palette" option in the save dialog the correct palette is applied and the colours look better on the Amiga screen. I also limit the colours to 256 and tick the "dither" option". Although further testing may prove that, that isn't necessary. I have found that if you save as 16 colours, even if your Amiga is displaying at 16 colours the image looks better if it's a 256 colour one? Presumably the Amiga's screen routine handles the colours better than Ultimate Paint does?

If anyone reading this wants to get Ultimate Paint you can get it here:

http://www.ultimatepaint.com/download.php

Siv
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Old 16 March 2020, 22:25   #11
DamienD
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On the PC I use PaintShop Pro for all resizing, and then cropping if required.

I then use XnView MP to change any colour depth etc. and finally save as an .IFF.
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Old 16 March 2020, 22:29   #12
Sivee
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@DamienD,

Thanks for the tip I will download and have a look at that.

Siv
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Old 16 March 2020, 23:23   #13
Sivee
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@DamienD,

Wow, brilliant program and it runs on Linux (my main OS) as well so no need to swap between Linux and Windows in my VM! Now I can do everything in Linux without a load of swapping about!

Thanks very much for recommending that application.

Siv
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Old 16 March 2020, 23:41   #14
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Old 17 March 2020, 15:21   #15
brian_p
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Quote:
Originally Posted by Sivee View Post
Hi,
I am trying to take an image in jpeg format off my PC and convert it to an IFF file as a desktop background image on the Amiga. I processed the image on the PC first so that it was 640 x 256 in dimension using Paint.net and then loaded it into Ultimate Paint. The reason for that being that Ultimate Paint can save to IFF format. I have found if I use the "Adaptive w /palette" option and set the colours to 256 it looks colour wise and quality wise on the Amiga as pretty much the same as the original JPG. However, when I load the image to the background on the Amiga it looks stretched in the vertical direction.


Here are the two images shown side by side on my website (sivill.com):


Images side by side


Is there a way I can manipulate the image so that when displayed on the Amiga (or WinUAE) that it looks correctly proportioned?


Graham Sivill



I take it you use PAL Highres... it uses doubleheight pixels. So take the picture you want and shrink/crop the image to fit 640x512. Then shrink that picture to 640x256 and it will be displayed correctly.
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