PL4 watermarking — problem with transparency when scaling

I’ve noticed a problem with image watermarks that contain transparency. It appears as if the transparency is not being scaled properly, leading to visibly jagged edges even at normal viewing sizes.

I created a Creative Commons logotype showing four of the circular symbols in a row and saved this as a 320px high PNG with transparency. Normally, in a graphics program such as Affinity Photo, scaling this down would lead to very smooth, if slightly blurry shapes. But when rendered at scale “5” on my image in PL4 it doesn’t look great. I noticed this because the symbols were visibly not smooth even when I was viewing the final output which was itself downscaled.

I can see non-white pixels which appear to show through the background colours, indicating that the transparency is being scaled, but poorly.

As rendered by PL4 (screen capture from Customize module, but also like this in final output).

The same source image as scaled by Affinity Photo using its simplest (Bilinear) scaling algorithm (size and background approximated).

Text watermarks also do not appear to be as smooth as I think they could be, though there is some anti-aliasing there too, from what I can see.

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Watermarking is a welcome addition but I too have also noticed this behaviour when adding a png watermark of my signature. It works fine with other applications.

I see a problem with the way of doing DPL.
The text or logo is integrated before the image processing and therefore the sharpness of this one depends on the output size of the image.
It would have been better to integrate it into the image after the process.

I don’t think the sequencing matters. PL will do a fine job of scaling sharp lines in a high megapixel image down to a smaller scale, so even if baked in at full size this problem should not occur. I believe it is the scaling directly applied to the watermark that is problematic.

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@sgospodarenko is there any official word on whether this is recognised as an issue?

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Hello @zkarj,

I have no connection to the MAC part. Please, tag either @akarlovsky or @SebinParis for such questions.

Regards,
Svetlana G.

@akarlovsky, @SebinParis are there any solutions to this, please? I waited with great anticipation for this feature but, in use, my png logo becomes pixelated, as @zkarj points out. Like others, I’d like to hear of any progress on this, please.I’ve uploaded screenshots of the png and the resulting watermark. Thanks, Mike

![Screen Shot 2021-01-17 at 6.34.15 pm|690x160, 75%](upload://d5KVqzJ1XBcclerfWSBSyQHZrij.jScreen Shot 2021-01-17 at 6.09.50 pm

peg)

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I too am having the watermark “jagged” issue. Has DXO replied with a resolution to this problem? Right now I have to apply watermarks using an external process. No bueno. Thanks.

Hello there,

I made a few tests (see attachment below) and I didn’t find any issues so far.

But here are a few considerations I’d like to highlight:

• the watermark image is applied to the image you see in the viewer, meaning that if you put a png with a 1000px width and then export the image without resizing, the watermark will be 1000px in width (expected)

• …but, if in the export window you decide to resize your image, PL will scale everything. Let’s say that you export your image at half the original size, the watermark will have a width of 500px in the output image (expected)

• If when exporting, the original image is considerably resized, you may encounter some scaling issues (expected too).

Regarding the last point, try opening a PNG in your favorite bitmap editing software (PS, AP…), then resize it considerably (like to 10-15% of its original size) and you’ll get an average-quality smaller PNG (because of the interpolation after such a significant size change).

So, if you intend to export your image with WM at a smaller size at the end, I’d suggest you to create dedicated presets in the Watermark tool, to get the better quality out of it (e.g. “My WM 1024px width”, “My WM 2048px width” and so on). You’ll fine-tune your WM in the viewer with an image that has the same output size you’d like to have, then save it as a preset. When exporting your original image, choose the resize options and the corresponding WM preset for a perfect output…

One final word about how to prepare the “best possible” PNG…Most software (basically all), when exporting a bitmap, they crop the output to the last existing pixel, BUT, this is a known issue which can affect the final (interpolated) quality of the image if one decides to resize it afterwards…

I’ll explain myself: as you can see below, the “WM crop 1.png” is what Adobe Illustrator has exported as a PNG (the original file in Illustrator was an EPS, a vector format). The output was cut to the last visible pixel.

In the second file (“WM crop 2.png”) I have exported the PNG with a “safety margin” all around.

As explained a few lines above, resizing a bitmap image “with a tight crop” often results with pixels close to the edge to appear like “crushed”, while applying the same scaling factor to the same image which has a “safety margin” all around, would not create such issue.
I hope I made myself clear enough :wink:

WM crop 1
WM crop 2

Steven.

Surely the 1000px versus 500px assertion is only true if the watermark is at “original scale”? As has been discussed in these forums previously, we do not know what the “Scale” slider value actually means (although it appears to be a relative proportion of the photo dimension). For the purposes of smooth scaling I created my watermark image at significant size.

In PhotoLab, I can set my 1360 x 320 pixel image to “50” scale and it looks very smooth at the approximate 800 x 188 pixel size resulting from my monitor and window sizes. Yet for normal use I have it set at “5” scale. Therefore, there is more than enough pixel data to provide superb definition when scaled even smaller on output.

If I am reading your descriptions correctly, it infers that @Franky was correct in that the watermark image is first scaled according to the Scale slider and then scaled again as part of the export scaling of the whole the image. Thus all the pixel data I created has been thrown away because I did not create at ‘the correct scale’ for my output. But if that is the case, I would like to understand why the Scale slider is not relative to the watermark image itself, but apparently to the photo as a whole?

As I illustrated in my original post, if my watermark image is scaled from original directly to the final output size (using my favourite bitmap software Affinity Photo), a very smooth result is possible. If I have to create different sized watermarks for all possible output sizes then the feature becomes a whole lot less useful.

The real issue here is that Export resizing is the only way to get output from PhotoLab at a given size. I get that noise reduction, chromatic aberration, sharpness etc can only realistically be processed at the full size of the image but the watermarks are add-on content that do not rely on the original image scale or data at all.

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You said: “The real issue here is that Export resizing is the only way to get output from PhotoLab at a given size”. Question: how do you envision to output an image to a different size (then the original) other than choosing it at the export stage? :thinking:

It’s not a feature I expect from PhotoLab, but it can be done in any pixel editing app. It’s usually simply called “resize” which can be done ahead of any export action.

But my point is that we have no means of affecting the scaling behaviour of PhotoLab and seeing the results ahead of export time.

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“…it can be done in any pixel editing app”. This is the whole point :wink:
Even if sometimes lines seem a bit blurry between “RAW editing vs bitmap editing” (e.g. even if the clone tool is on the edge, PL, LR, C1 and all the others are not bitmap editing software…).

Right. So we need PL to “do the right thing”. Which in my view is to composite the watermarks, appropriately scaled once, at the final output size.

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This same issue affects the windows version for what it’s worth.
My watermark is typically reduced a lot but exactly how much depends on the output crop.
Capture One produces a very nice, smoothly scaled watermark. The DXO version really looks terrible by comparison. C1 and DXO are both producing the same size watermark with the same source transparent PNG.

For sure it can and should be improved.

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Is it dumb to ask that we can use a vector format for the watermark? I mean, I have spent quite an amount of time to create a logo that I like, and the whole bitmap resizing has simply destroyed it all its beauty in all the pictures where this option was applied — I use a third-party software to add my logo after-the-fact now, which does a much much better job, and I don’t think it’s normal…

An interesting idea. I just presumed a very large sized watermark properly resized would be good enough and very simple. It’s just the resizing is done poorly.

I have mostly moved away from Capture One but I use it for all my watermarking. Pretty sad actually but true.

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Hi,

Just read this topic and stayed completly stunned.
So DxO is unable to do clean scale of a bitmap image, and DxO staf guys justify that @StevenL ?
Is it that bad ?
Surrealist !!!

That sounds like a great idea but would not solve what we (the users) believe to be the problem, as the watermark is scaled twice — once to the required scale on the ‘full sized’ image and then again as part of the overall scaling done at export.

So with a vector watermark the first scaling would be great, but the second one would introduce the same problem, and this is borne out by the similar issue experienced with a text watermark which is already vector-based.

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