package apple2 import ( "image" "image/color" ) const ( doubleHiResWidth = 2 * hiResWidth ) func snapshotDoubleHiResModeMono(a *Apple2, isSecondPage bool, getNTSCMask bool, light color.Color) (*image.RGBA, *image.Alpha) { // As described in "Inside the Apple IIe" size := image.Rect(0, 0, doubleHiResWidth, hiResHeight) img := image.NewRGBA(size) // To support RGB-mode 14 we will have a mask to mark where we should not have the NTSC filter applied // See: https://apple2online.com/web_documents/Video-7%20Manual%20KB.pdf var ntscMask *image.Alpha if getNTSCMask { ntscMask = image.NewAlpha(size) } for y := 0; y < hiResHeight; y++ { lineParts := [][]uint8{ getHiResLine(a, y, isSecondPage, true /*auxmem*/), getHiResLine(a, y, isSecondPage, false /*auxmem*/), } x := 0 // For the NTSC filter to work we have to insert an initial black pixel and skip the last one ¿? img.Set(x, y, color.Black) if getNTSCMask { ntscMask.Set(x, y, color.Opaque) } x++ for iByte := 0; iByte < hiResLineBytes; iByte++ { for iPart := 0; iPart < 2; iPart++ { b := lineParts[iPart][iByte] mask := color.Transparent // Apply the NTSC filter if getNTSCMask && b&0x80 == 0 { mask = color.Opaque // Do not apply the NTSC filter } for j := uint(0); j < 7; j++ { // Set color bit := (b >> j) & 1 colour := light if bit == 0 { colour = color.Black } img.Set(x, y, colour) // Set mask if requested if getNTSCMask { ntscMask.Set(x, y, mask) } x++ } } } } return img, ntscMask }