// uninterlace rearranges the pixels in m to account for interlaced input.
func uninterlace(m *image.Paletted) {
var nPix []uint8
dx := m.Bounds().Dx()
dy := m.Bounds().Dy()
nPix = make([]uint8, dx*dy)
offset := 0 // steps through the input by sequential scan lines.
for _, pass := range interlacing {
nOffset := pass.start * dx // steps through the output as defined by pass.
for y := pass.start; y < dy; y += pass.skip {
copy(nPix[nOffset:nOffset+dx], m.Pix[offset:offset+dx])
offset += dx
nOffset += dx * pass.skip
}
}
m.Pix = nPix
}
func (d *decoder) uninterlace(m *image.Paletted) {
if d.imageFields&ifInterlace == 0 {
return
}
var nPix []uint8
dx := d.width
dy := d.height
nPix = make([]uint8, dx*dy)
offset := 0 // steps through the input by sequentical scan lines.
for _, pass := range interlacing {
nOffset := pass.start * dx // steps through the output as defined by pass.
for y := pass.start; y < dy; y += pass.skip {
copy(nPix[nOffset:nOffset+dx], m.Pix[offset:offset+dx])
offset += dx
nOffset += dx * pass.skip
}
}
m.Pix = nPix
}