Creating a Watermark about scrimage HOT 14 CLOSED

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

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So here is my outup
Main image:

Watermark:

RESULT:

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

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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.

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

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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 ?

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

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

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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

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

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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)

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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")

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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.

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

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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.

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