func hBitmapFromImage(im image.Image) (win.HBITMAP, error) {
var bi win.BITMAPV5HEADER
bi.BiSize = uint32(unsafe.Sizeof(bi))
bi.BiWidth = int32(im.Bounds().Dx())
bi.BiHeight = -int32(im.Bounds().Dy())
bi.BiPlanes = 1
bi.BiBitCount = 32
bi.BiCompression = win.BI_BITFIELDS
// The following mask specification specifies a supported 32 BPP
// alpha format for Windows XP.
bi.BV4RedMask = 0x00FF0000
bi.BV4GreenMask = 0x0000FF00
bi.BV4BlueMask = 0x000000FF
bi.BV4AlphaMask = 0xFF000000
hdc := win.GetDC(0)
defer win.ReleaseDC(0, hdc)
var lpBits unsafe.Pointer
// Create the DIB section with an alpha channel.
hBitmap := win.CreateDIBSection(hdc, &bi.BITMAPINFOHEADER, win.DIB_RGB_COLORS, &lpBits, 0, 0)
switch hBitmap {
case 0, win.ERROR_INVALID_PARAMETER:
return 0, newError("CreateDIBSection failed")
}
// Fill the image
bitmap_array := (*[1 << 30]byte)(unsafe.Pointer(lpBits))
i := 0
for y := im.Bounds().Min.Y; y != im.Bounds().Max.Y; y++ {
for x := im.Bounds().Min.X; x != im.Bounds().Max.X; x++ {
r, g, b, a := im.At(x, y).RGBA()
bitmap_array[i+3] = byte(a >> 8)
bitmap_array[i+2] = byte(r >> 8)
bitmap_array[i+1] = byte(g >> 8)
bitmap_array[i+0] = byte(b >> 8)
i += 4
}
}
return hBitmap, nil
}
func NewBitmap(size Size) (bmp *Bitmap, err error) {
var hdr win.BITMAPINFOHEADER
hdr.BiSize = uint32(unsafe.Sizeof(hdr))
hdr.BiBitCount = 24
hdr.BiCompression = win.BI_RGB
hdr.BiPlanes = 1
hdr.BiWidth = int32(size.Width)
hdr.BiHeight = int32(size.Height)
err = withCompatibleDC(func(hdc win.HDC) error {
hBmp := win.CreateDIBSection(hdc, &hdr, win.DIB_RGB_COLORS, nil, 0, 0)
switch hBmp {
case 0, win.ERROR_INVALID_PARAMETER:
return newError("CreateDIBSection failed")
}
bmp, err = newBitmapFromHBITMAP(hBmp)
return err
})
return
}