ebiten: add (*Image).ReadPixels

Closes #1995
This commit is contained in:
Hajime Hoshi 2022-08-08 01:05:55 +09:00
parent 72d5002e72
commit 81bd5b488c
3 changed files with 57 additions and 9 deletions

View File

@ -777,6 +777,37 @@ func (i *Image) ColorModel() color.Model {
return color.RGBAModel return color.RGBAModel
} }
// ReadPixels reads the image's pixels from the image.
//
// ReadPixels loads pixels from GPU to system memory if necessary, which means that ReadPixels can be slow.
//
// ReadPixels always sets a transparent color if the image is disposed.
//
// len(pixels) must be 4*width*height. If the sizes don't match, ReadPixels returns an error.
//
// Note that an important logic should not rely on values returned by ReadPixels, since
// the returned values can include very slight differences between some machines.
//
// ReadPixels can't be called outside the main loop (ebiten.Run's updating function) starts.
func (i *Image) ReadPixels(pixels []byte) error {
b := i.Bounds()
if got, want := len(pixels), 4*b.Dx()*b.Dy(); got != want {
return fmt.Errorf("ebiten: len(pixels) must be %d but %d at ReadPixels", want, got)
}
if i.isDisposed() {
for i := range pixels {
pixels[i] = 0
}
return nil
}
i.resolveSetVerticesCacheIfNeeded()
x, y := i.adjustPosition(b.Min.X, b.Min.Y)
return i.image.ReadPixels(pixels, x, y, b.Dx(), b.Dy())
}
// At returns the color of the image at (x, y). // At returns the color of the image at (x, y).
// //
// At loads pixels from GPU to system memory if necessary, which means that At can be slow. // At loads pixels from GPU to system memory if necessary, which means that At can be slow.
@ -819,9 +850,7 @@ func (i *Image) at(x, y int) (r, g, b, a byte) {
if c, ok := i.setVerticesCache[[2]int{x, y}]; ok { if c, ok := i.setVerticesCache[[2]int{x, y}]; ok {
return c[0], c[1], c[2], c[3] return c[0], c[1], c[2], c[3]
} }
var pix [4]byte return i.image.At(x, y)
i.image.ReadPixels(pix[:], x, y, 1, 1)
return pix[0], pix[1], pix[2], pix[3]
} }
// Set sets the color at (x, y). // Set sets the color at (x, y).

View File

@ -110,6 +110,21 @@ func TestImagePixels(t *testing.T) {
} }
} }
} }
pix := make([]byte, 4*w*h)
if err := img0.ReadPixels(pix); err != nil {
t.Fatal(err)
}
for j := 0; j < h; j++ {
for i := 0; i < w; i++ {
idx := 4 * (j*w + i)
got := color.RGBA{pix[idx], pix[idx+1], pix[idx+2], pix[idx+3]}
want := color.RGBAModel.Convert(img.At(i, j))
if got != want {
t.Errorf("(%d, %d): got %v; want %v", i, j, got, want)
}
}
}
} }
func TestImageComposition(t *testing.T) { func TestImageComposition(t *testing.T) {

View File

@ -75,21 +75,25 @@ func (i *Image) ReplacePixels(pix []byte, x, y, width, height int) {
i.mipmap.ReplacePixels(pix, x, y, width, height) i.mipmap.ReplacePixels(pix, x, y, width, height)
} }
func (i *Image) ReadPixels(pixels []byte, x, y, width, height int) { func (i *Image) ReadPixels(pixels []byte, x, y, width, height int) error {
// Check the error existence and avoid unnecessary calls. return theUI.readPixels(i.mipmap, pixels, x, y, width, height)
if theGlobalState.error() != nil {
return
} }
if err := theUI.readPixels(i.mipmap, pixels, x, y, width, height); err != nil { func (i *Image) At(x, y int) (r, g, b, a byte) {
// Check the error existence and avoid unnecessary calls.
if theGlobalState.error() != nil {
return 0, 0, 0, 0
}
var pix [4]byte
if err := theUI.readPixels(i.mipmap, pix[:], x, y, 1, 1); err != nil {
if panicOnErrorOnReadingPixels { if panicOnErrorOnReadingPixels {
panic(err) panic(err)
} }
theGlobalState.setError(err) theGlobalState.setError(err)
for i := range pixels { return 0, 0, 0, 0
pixels[i] = 0
}
} }
return pix[0], pix[1], pix[2], pix[3]
} }
func (i *Image) DumpScreenshot(name string, blackbg bool) error { func (i *Image) DumpScreenshot(name string, blackbg bool) error {