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var blit = (function(){
var blit = {}
blit.and = blit.atop = function(A, B, x, y){
x = x || 0 ; y = y || 0
B.forEach(function(lex, u, v){
var cell = A.getCell(u+x, v+y)
if (cell && lex.opacity > 0) {
cell.assign(lex)
}
})
}
blit.or = blit.under = function(A, B, x, y){
x = x || 0 ; y = y || 0
B.forEach(function(lex, u, v){
var cell = A.getCell(u+x, v+y)
if (cell && cell.opacity == 0) {
cell.assign(lex)
}
})
}
// copy the region of A beginning at x,y into B
blit.copy_from = function(A, B, x, y){
x = x || 0 ; y = y || 0
B.forEach(function(lex, u, v){
var cell = A.getCell(u+x, v+y)
if (cell) {
lex.assign(cell)
}
})
}
blit.copy_toroidal_from = function(A, B, x, y){
x = x || 0 ; y = y || 0
B.forEach(function(lex, u, v){
var cell = A.get(u+x, v+y)
if (cell) {
lex.assign(cell)
}
})
}
blit.copy_to = function(A, B, x, y){
x = x || 0 ; y = y || 0
B.forEach(function(lex, u, v){
var cell = A.getCell(u+x, v+y)
if (cell) {
cell.assign(lex)
}
})
}
blit.invert = function(A, B, x, y){
x = x || 0 ; y = y || 0
B.forEach(function(lex, u, v){
var cell = A.getCell(u+x, v+y)
if (cell && lex.opacity > 0) {
cell.fg = get_inverse(cell.fg)
cell.bg = get_inverse(cell.bg)
}
})
}
var distance_rect = function(x, y, ratio){
return Math.sqrt((Math.pow(y * ratio, 2)) + Math.pow(x, 2))
}
var distance_square = function(x, y, ratio){
return Math.sqrt((Math.pow(y * ratio, 2)) + Math.pow(x * ratio, 2))
}
blit.circle = function(A, lex){
var hw = brush.w/2, hh = brush.h/2
var ratio, distance
if (brush.w === brush.h){
distance = distance_square
ratio = hw / hh * (brush.w === 3 || brush.w === 5 ? 1.2 : 1.05)
} else {
distance = distance_rect
ratio = hw / hh
}
A.forEach(function(lex,x,y) {
if (distance(x - hw + 0.5, y - hh + 0.5, ratio) > hw){
lex.clear()
}
})
}
blit.cross = function(A, lex){
A.forEach(function(lex,x,y) {
if ((x+y)%2) {
lex.clear()
}
})
}
blit.inverted_cross = function(A, lex){
// 1x1 brush should still draw something
if (A.w == 1 && A.h == 1) {
return
}
A.forEach(function(lex,x,y) {
if (!((x+y)%2)) {
lex.clear()
}
})
}
blit.square = function(A, lex){
// i.e. no transparency
}
return blit
})()
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