first.go

src, _ := loadBaseImageForPost(post)
img := image.NewRGBA(src.Bounds())
gc := draw2dimg.NewGraphicContext(img)

gc.DrawImage(src)

// Draw title
gc.SetFillColor(color.RGBA{0xff, 0xff, 0xff, 0xff})
gc.SetFontSize(26)
gc.FillStringAt(post.Title, 140, 81.5)

// Draw content
gc.SetFillColor(color.RGBA{0x32, 0x32, 0x32, 0xff})
gc.SetFontSize(26)
gc.FillStringAt(post.Content, 60, 190)

// Draw forum
forum := post.ForumName
_, _, right, _ := gc.GetStringBounds(forum)
gc.SetFillColor(color.RGBA{0xff, 0xff, 0xff, 0xff})
gc.SetFontSize(26)
gc.FillStringAt(forum, 1140-right, 81.5)

// Draw time
timeLocation, _ := time.LoadLocation("Asia/Taipei")
time := post.CreatedAt.In(timeLocation).Format("2006/1/2 15:04")
_, _, right, bottom := gc.GetStringBounds(time)
gc.SetFillColor(color.RGBA{0x79, 0x79, 0x79, 0xff})
gc.SetFontSize(26)
gc.FillStringAt(time, 1140-right, 510-bottom)

ctx.Response.Header.Set("Content-Type", "image/png")
png.Encode(ctx, img)