# SpritePixels
A 2D pixel buffer used as the output of the software 3D rasterizer.
Holds RGBA pixels in ABGR format (matching Simba's PColorBGRA / TImage),
with width and height matching the target buffer size (36 × 32 for items).

Methods:
  DrawBorder(color) — draws an outline around non-transparent pixels.
  DrawShadow(color) — draws a drop shadow behind non-transparent pixels.
  ToImage()           — converts the buffer to a Simba TImage with full alpha.


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## SpritePixels.Create
```pascal
function TSpritePixels.Create(w, h: Integer): TSpritePixels; static;
```
An empty, fully transparent pixel buffer.


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## SpritePixels.DrawBorder
```pascal
procedure TSpritePixels.DrawBorder(color: Integer);
```
Outlines the drawn pixels, colouring every transparent pixel that touches one of them on any of
its four sides.

It builds a second buffer rather than writing in place, so that the outline it is adding does
not itself count as a neighbour and grow outwards.


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## SpritePixels.DrawShadow
```pascal
procedure TSpritePixels.DrawShadow(color: Integer);
```
Casts a one pixel shadow down and to the right of the drawn pixels.

This one does work in place, walking from the bottom right corner backwards so that a pixel it
writes is never read again as a source.


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## SpritePixels.Overlay
```pascal
procedure TSpritePixels.Overlay(const sprite: TSpritePixels);
```
Draws `sprite` on top of this buffer, skipping its transparent pixels. Both buffers must be the
same size and both must have had {ref}`TSpritePixels.DrawBorder` called on them.

`Border` and `Mask` follow what ends up visible: every pixel `sprite` covers takes `sprite`'s
border in place of this buffer's, and becomes part of the mask if it was not already.


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## SpritePixels.DrawAtOn
```pascal
procedure TSpritePixels.DrawAtOn(var graphics: TGraphics3D; x, y: Integer);
```
Copies this buffer onto a rasterizer's buffer at `x, y`, clipped to its draw region and skipping
transparent pixels.


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## SpritePixels.ToImage
```pascal
function TSpritePixels.ToImage(): TImage;
```
The buffer as an image with proper transparency.

Nothing has to be converted here. The rasterizer draws through `ColorUtils.Palette`,
whose entries are already in the order `TImage.FromData` reads and already carry a full alpha
byte, so a pixel that was drawn is opaque and a pixel that was never touched is still zero -
transparent, which is exactly how the original client turns its buffers into images.


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## SpritePixels.BorderImage
```pascal
function TSpritePixels.BorderImage(): TImage;
```
Get an image of the sprite border.


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## SpritePixels.MaskImage
```pascal
function TSpritePixels.MaskImage(): TImage;
```
Get an image of the sprite mask.
Basically an image of the item fully white to mask it's background.