"Invalid filter" error is thrown when loading a PNG image.

As we discussed in the mailing list, an "Invalid Filter" error is thrown when loading the PNG at the bottom of this post. The error is thrown by this piece of code :

https://github.com/HaxeFoundation/format/blob/master/format/png/Tools.hx

``` haxe
inline function decodeLine(y, f, getValue) {
switch( f ) {
case 0:
for( x in 0...width ) {
decode(getValue);
bgra.set(w++,vb);
bgra.set(w++,vg);
bgra.set(w++,vr);
bgra.set(w++,va);
}
case 1:
var cr = 0, cg = 0, cb = 0, ca = 0;
for( x in 0...width ) {
decode(getValue);
cb += vb; bgra.set(w++,cb);
cg += vg; bgra.set(w++,cg);
cr += vr; bgra.set(w++,cr);
ca += va; bgra.set(w++,ca);
bgra.set(w++, va);
}
case 2:
var stride = y == 0 ? 0 : width * 4;
for( x in 0...width ) {
decode(getValue);
bgra.set(w, vb + bgra.get(w - stride)); w++;
bgra.set(w, vg + bgra.get(w - stride)); w++;
bgra.set(w, vr + bgra.get(w - stride)); w++;
bgra.set(w, va + bgra.get(w - stride)); w++;
}
case 3:
var cr = 0, cg = 0, cb = 0, ca = 0;
var stride = y == 0 ? 0 : width * 4;
for( x in 0...width ) {
decode(getValue);
cb = (vb + ((cb + bgra.get(w - stride)) >> 1)) & 0xFF; bgra.set(w++, cb);
cg = (vg + ((cg + bgra.get(w - stride)) >> 1)) & 0xFF; bgra.set(w++, cg);
cr = (vr + ((cr + bgra.get(w - stride)) >> 1)) & 0xFF; bgra.set(w++, cr);
cr = (va + ((ca + bgra.get(w - stride)) >> 1)) & 0xFF; bgra.set(w++, ca);
}
case 4:
var stride = width * 4;
var cr = 0, cg = 0, cb = 0, ca = 0;
for( x in 0...width ) {
decode(getValue);
cb = (filter(bgra, x, y, stride, cb, w) + vb) & 0xFF; bgra.set(w++, cb);
cg = (filter(bgra, x, y, stride, cg, w) + vg) & 0xFF; bgra.set(w++, cg);
cr = (filter(bgra, x, y, stride, cr, w) + vr) & 0xFF; bgra.set(w++, cr);
ca = (filter(bgra, x, y, stride, ca, w) + va) & 0xFF; bgra.set(w++, ca);
}
default:
throw "Invalid filter "+f;
}
}
```

The error occur when loading the PNG with Heaps.