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Bitmap image conversions

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3 hours ago, Tursi said:

Looks great! For the astronaut one, you have a bit of black border at the left which is causing the first column of pixels to look stretched (as the black is considered more important to preserve than the detail in the moon's surface) - crop out the black border and it should convert better. 

First, I added a bunch more, with links to the source at APOD, plus 9918A versions.

 

I checked the astronaut picture, and the black border comes in because the image is 509 x 385. I had to crop out some white pixels on the edges.

Is the black bar just filling empty space then?

 

Here's some details of that one, before and after Convert9918:

 

plum_apollo16_big_crop_hist0.png.600ed03178cd8f3e8cef6ae12c1c29f1.png     plum_apollo16_big_crop_hist1.png.d917ea04dc0a005bc79595b5f18a0f44.png

 

 

 

 

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10 hours ago, FarmerPotato said:

I checked the astronaut picture, and the black border comes in because the image is 509 x 385. I had to crop out some white pixels on the edges.

Is the black bar just filling empty space then?

The new pics and the comparisons are nice! I know about APOD. :)

 

Yes on the sizing. Convert9918 will take whatever image you give it, and resize it to fit according to the "Fill Mode".

 

In "Default", the entire image is scaled to fit on the screen, with black bars filling the remains. If you watch the text output, you'll see that it checks each dimension, then checks the larger scale, scaling both axes by it. 509x385 will probably size to 253x192, leaving 3 pixels to be filled to get 256 across.

 

Generally, I prefer to crop the image to get more pixels, and that's what the other three modes do: Top/Left, Middle, and Bottom/Right just specify which part of the image you want to focus on. Most of the time you want "Middle", but Top/Left is usually good for portraits. This uses the smaller scale of the two axes, and lets the other axis hang off the edge to give you more pixels in the image -- in effect this fills the screen.

 

Alternately, for finer control, crop the image in your favorite PC tool then resize to 256x192, and the tool will know that no resize is needed. :)

 

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I updated Convert9918 last night after seeing the results @Asmusr gets with his 4x1 pseudo-mode. I already had a color-only conversion mode, but it only used the background color, giving 8x1. (There was a reason for that, but I didn't like the results so I didn't take it any further). Now it does the 4x1, with the assumption the pattern table is loaded as all 0xF0, and the results are not bad at all. So the advantage is that the image only needs 6k of data (you still need all the tables in VDP, of course, I haven't looked at how much the masking might help, if it does).

 

image.thumb.png.98d6b8aee00d0ec14eb4225d5755d862.png

image.thumb.png.8fe8932f5078aa9d3c09c14ebf0df686.png

image.thumb.png.6a52d8cd0c316420fa220d98ab4336dc.png

 

Would this have allowed a full-screen Dragon's Lair? It's the same amount of data, but... I think the answer is "not quite". It does result in a loss of resolution which is really too much. DL shipped with a horizontal resolution of 192, but this is only 64.

 

image.thumb.png.88104f318a7b4abe56731b8ffe8dc7eb.png

 

As always: http://harmlesslion.com/software/convert9918

 

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