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Old 17 September 2016, 23:59   #1
mark_k
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Join Date: Aug 2004
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Pre-scaling before bilinear filtering for less-blurry image

This is probably already possible by stacking filters. Can anyone explain how because I haven't been able to figure it out.

I've been using a 1024768-pixel Workbench. Text looks pretty small on my laptop, so I want to scale the image by 1.5 to have it occupy 15361152 pixels on-screen. Setting Horiz. size and Vert. size to 1.5 in Filter Settings works, but the result is pretty blurry.

However, if I could pre-scale the image (e.g. pixel-doubling to 20481536 then scaling down with filtering to 15361152) the result would be significantly sharper. See the attached images.

The blurrier scaled-up-1.5 image was created using a paint package rather than getting a screenshot of the filtered/scaled image in WinUAE. But it looks pretty similar. The other one was also made using a paint package, scaling up 2 then down with bilinear filtering.

[After clicking a thumbnail, click the image to (hopefully) show it unscaled in your web browser.]
Attached Thumbnails
Click image for larger version

Name:	WB_1024x768.png
Views:	95
Size:	14.6 KB
ID:	50010   Click image for larger version

Name:	Scale_up_1.5x_to_1536x1152.png
Views:	88
Size:	59.9 KB
ID:	50011   Click image for larger version

Name:	Scale_up_2x_down_to_1536x1152.png
Views:	99
Size:	35.5 KB
ID:	50012  
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