make atlas

atlas.nim

import sdl2
import sdl2.image
import os
import strutils

if not sdl2.init(INIT_EVERYTHING):
  quit "Failed start SDL2"

if image.init(IMG_INIT_PNG) == -1:
  quit "Failed start SDL2_Image"

const size = 1024

var rmask = uint32(0xff000000)
var gmask = uint32(0x00ff0000)
var bmask = uint32(0x0000ff00)
var amask = uint32(0x000000ff)
var atlasImage = createRGBSurface(
  0,
  cint(size),
  cint(size),
  32,
  rmask,
  gmask,
  bmask,
  amask
)

var r = Rect((x:cint(0), y:cint(0), w:cint(size), h:cint(size)))
fillRect(
  atlasImage,
  addr r,
  uint32(0)
)

var heights : array[size, uint16]
var margin = 8

proc putImage(file: string): void = 
  echo file
  var image: SurfacePtr = load(file)
  if image == nil:
    echo "Failed to load ", file

  var imgWidth = image.w + margin * 2
  var imgHeight = image.h + margin * 2

  echo imgWidth, imgHeight

  var lowest = size
  var at = 0
  for i in 0..size - 1:
    var v = int(heights[i])
    if v < lowest:
      # found low point, is it consecutive?
      var fit = true
      for j in 0 .. imgWidth:
        if i + j >= size:
          fit = false
          break
        if int(heights[i + j]) > v:
          fit = false
          break
      if fit:
          # found!
          lowest = v
          at = i
    
  if lowest + imgHeight > size:
    echo "Atlas is full!!!"

  for j in at..at + imgWidth - 1:
    heights[j] = uint16(lowest + imgHeight + margin * 2)

  echo "lowest", lowest, at
  var srcRect = Rect((x:cint(0), y:cint(0), w:cint(image.w), h:cint(image.h)))
  var dstRect = Rect((x:cint(at + margin), y:cint(lowest + margin), w:cint(image.w), h:cint(image.h)))

  blitSurface(
    image, 
    addr srcRect,
    atlasImage,
    addr dstRect
  )

for file in walkDirRec("data"):
  if file.endsWith(".png"):
    putImage(file)    

# proc savePNG*(surface: SurfacePtr, file: cstring): cint {.importc: "IMG_SavePNG".}
discard savePNG(atlasImage, "bin/atlas.png")