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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package widget
import (
// TODO: mask and maskPoint, not just src and srcRect.
// TODO: be able to specify the draw operator: Src instead of Over.
// TODO: if the measured size differs from the actual size, specify a
// background color (or tile-able image like a checkerboard)? Specify a
// draw.Scaler from the package? Be able to center the
// source image within the widget?
// Image is a leaf widget that paints an image.Image.
type Image struct {
Src image.Image
SrcRect image.Rectangle
// NewImage returns a new Image widget for the part of a source image defined
// by src and srcRect.
func NewImage(src image.Image, srcRect image.Rectangle) *Image {
w := &Image{
Src: src,
SrcRect: srcRect,
w.Wrapper = w
return w
func (w *Image) Measure(t *theme.Theme, widthHint, heightHint int) {
w.MeasuredSize = w.SrcRect.Size()
func (w *Image) PaintBase(ctx *node.PaintBaseContext, origin image.Point) error {
if w.Src == nil {
return nil
// wRect is the widget's layout rectangle, in dst's coordinate space.
wRect := w.Rect.Add(origin)
// sRect is the source image rectangle, in dst's coordinate space, so that
// the upper-left corner of the source image rectangle aligns with the
// upper-left corner of wRect.
sRect := w.SrcRect.Add(wRect.Min.Sub(w.SrcRect.Min))
draw.Draw(ctx.Dst, wRect.Intersect(sRect), w.Src, w.SrcRect.Min, draw.Over)
return nil