// NewScreenshot will take a screenshot of the screen and convert it to an image.Image
func NewScreenshot() image.Image {
// Temporarily unbind the currently active canvas (glReadPixels reads the active framebuffer, not the main one.)
canvases := GetCanvas()
SetCanvas()
w, h := int32(screen_width), int32(screen_height)
screenshot := image.NewRGBA(image.Rect(0, 0, int(w), int(h)))
stride := int32(screenshot.Stride)
pixels := make([]byte, len(screenshot.Pix))
gl.ReadPixels(pixels, 0, 0, int(w), int(h), gl.RGBA, gl.UNSIGNED_BYTE)
// OpenGL sucks and reads pixels from the lower-left. Let's fix that.
for y := int32(0); y < h; y++ {
i := (h - 1 - y) * stride
copy(screenshot.Pix[y*stride:], pixels[i:i+w*4])
}
// Re-bind the active canvas, if necessary.
SetCanvas(canvases...)
return screenshot
}
// NewImageData will create an image from the canvas data. It will return an error
// only if the dimensions given are invalid
func (canvas *Canvas) NewImageData(x, y, w, h int32) (image.Image, error) {
if x < 0 || y < 0 || w <= 0 || h <= 0 || (x+w) > canvas.width || (y+h) > canvas.height {
return nil, fmt.Errorf("Invalid ImageData rectangle dimensions.")
}
prev_canvas := GetCanvas()
SetCanvas(canvas)
screenshot := image.NewRGBA(image.Rect(int(x), int(y), int(w), int(h)))
stride := int32(screenshot.Stride)
pixels := make([]byte, len(screenshot.Pix))
gl.ReadPixels(pixels, int(x), int(y), int(w), int(h), gl.RGBA, gl.UNSIGNED_BYTE)
for y := int32(0); y < h; y++ {
i := (h - 1 - y) * stride
copy(screenshot.Pix[y*stride:], pixels[i:i+w*4])
}
SetCanvas(prev_canvas...)
// The new ImageData now owns the pixel data, so we don't delete it here.
return screenshot, nil
}