Creating a Watermark

[igalbenardete]

I am trying to put watermarks on the images. I have tried half of the composite types but could not get the result I wanted. Composite combines the images but both images just appear faded or one just becomes completely dominated by the other and only a single image is visible. Is there an alternative for watermarks ? I found Watermarks.scala in the repository but could not make any sense out of it or use it.

[gwenzek]

Here is a sample of code for watermarking. I don't know why there is no 'Add' composite in scrimage, but you can add it easily:

import com.sksamuel.scrimage.Image
import com.sksamuel.scrimage.composite._
import thirdparty.romainguy.BlendComposite.BlendingMode
import thirdparty.romainguy.BlendComposite

object Main extends App {
  class AddComposite(alpha: Double) extends BlenderComposite(BlendComposite.BlendingMode.ADD, alpha.toFloat)

  val bird = Image(new java.io.File("bird_small.png"))
  val watermark = Image(new java.io.File("watermark.png"))

  val marked = bird.composite(new AddComposite(0.5), watermark)

  marked.write("bird_marked.png")
}

bird_small.png

watermark.png

bird_marked.png

[igalbenardete]

So here is my outup
Main image:

Watermark:

RESULT:

[igalbenardete]

By the way main image is jpeg and the watermark is png. Just letting you know so that that is not the problem, hopefully.

[gwenzek]

With the code I put above with an alpha value of 1 (new AddComposite(1.0)), I go this:

Which seems better (the car isn't altered). But if you are looking for a watermarking that can be use for a lot of images I wouldn't choose something with red in it.

[igalbenardete]

This one is good enough and these are just example images. However, my results are completely different:

[gwenzek]

I wasn't able to reproduce your result, but here is how I got mine:

import com.sksamuel.scrimage.Image
import com.sksamuel.scrimage.composite._
import thirdparty.romainguy.BlendComposite.BlendingMode
import thirdparty.romainguy.BlendComposite

object Main extends App {
  class AddComposite(alpha: Double) extends BlenderComposite(BlendComposite.BlendingMode.ADD, alpha.toFloat)

  val car = Image(new java.io.File("car.jpg"))
  val sold = Image(new java.io.File("sold.png"))

  val car_sold = car.composite(new AddComposite(1), sold)
  car_sold.write("car_sold.png")
}

Which composite and alpha parameter did you choose ?

[igalbenardete]

currentImage = currentImage.composite(new AddComposite(1.0), watermarkImage)

This is how I use it and I defined AddComposite same as here.

[gwenzek]

Really weird ...

Is their any other operation that you apply to your currentImage before or after that ?
because the result is bigger (800x600) than the car image (628x417) but it should be of the same size.

Indeed img.composite(..., other) is always of the size of img

[igalbenardete]

A resizing operation is applied before the composite function is called but that should not matter

[igalbenardete]

I fixed it. The watermark image is resized as well. When the resize function returns an image, it covers the background with white background. However the watermark png has a transparent background. Is there a way to avoid having a white background while using resize function ? Additionally, does the watermark image has to be transparent ? What if I want to make it completely opaque ? (This means that I just want to put one image on top of the other)

[gwenzek]

ok this is interesting.
I tested it and scale doesn't remove transparency. But there are operations that does remove it, like saving as JPEG and load back (JPEG doesn't handle transparency)

In my first example, I didn't use a transparent image, but an image with a black background, because it is 'transparent' respectively to the add composite.

If you just want to draw over, just use the overlay method: car.overlay(sold).write("car_sold_2.png")

[igalbenardete]

Ok perfect this looks like it is working. So the only difference between scaleTo and resize is basically the background handling ?
With the composite and using resize with a color with 0 alpha still does not make it work but I guess scaleTo will be just fine for now. Overlay was what I am looking for thank you very much.

[igalbenardete]

In resizeTo i was able to indicate a Position for the image, how can I do the same thing by using scaleTo ?

[gwenzek]

The readme provides a bit of information about this. resize doesn't scale your image so if you resize to a bigger image it will have to fill the background with the provided color (white by default).

overlay(overlayImage: Image, x: Int = 0, y: Int = 0): Image let you specify where you want to draw the overlayImage. I think that would be the way to go.