Golang : Set image canvas or background to transparent
Putting this down here for my own future reference. Maybe useful to you too. Anyway, basically what I need is to make an image canvas or background to transparent before drawing over it.
For example, I need to set the foreground color to black and set the background to transparent :
foreGroundColor := image.NewUniform(black)
backGroundColor := image.Transparent
backgroundWidth := 700
backgroundHeight := 50
background = image.NewRGBA(image.Rect(0, 0, backgroundWidth, backgroundHeight))
draw.Draw(background, background.Bounds(), backGroundColor, image.ZP, draw.Src)
// draw something with foreGroundColor.....
alternatively, this method will work as well.
// make every pixel transparent
for y := 0; y < backgroundHeight; y++ {
for x := 0; x < backgroundWidth; x++ {
background.Set(x, y, image.Transparent)
}
}
To test, save the background to a PNG file.
// Save that background image to PNG.
imgFile, err := os.Create("background.png")
if err != nil {
fmt.Println(err)
os.Exit(-1)
}
defer imgFile.Close()
buff := bufio.NewWriter(imgFile)
err = png.Encode(buff, background)
if err != nil {
fmt.Println(err)
os.Exit(-1)
}
err = buff.Flush()
if err != nil {
fmt.Println(err)
os.Exit(-1)
}
fmt.Println("Save to background.png")
Remember...... that JPEG does not support transparency.
Happy coding!
References:
https://www.socketloop.com/references/golang-image-alpha-set-and-setalpha-functions-examples
By Adam Ng
IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.
Advertisement
Tutorials
+6.5k Golang : Command line ticker to show work in progress
+7.9k Golang : Apply Histogram Equalization to color images
+24.8k Golang : Convert(cast) string to uint8 type and back to string
+17.4k Unmarshal/Load CSV record into struct in Go
+5k Golang : Function as an argument type example
+6.1k Golang : Array mapping with Interface
+10.7k Golang : Clean formatting/indenting or pretty print JSON result
+10.7k Golang : md5 hash of a string
+19.5k Golang : Clean up null characters from input data
+7.2k How to show different content from website server when AdBlock is detected?
+11.6k Golang : Transform comma separated string to slice example
+9.8k Golang : Removes punctuation or defined delimiter from the user's input