Image overlay inside cells

[knorrest]

I'm creating pdf:s with the library, using borderless nested pdf-tables to make it simple to place my content. My problem is that in addition to text and background, I would need to add image overlays inside some cells. In openpdf/itext such things seem to be done using cell events. Am I right in that there is no support for this in the library?

[yogthos]

Yeah, there's no support for hooking into cell events at the moment. I'd be open to a PR for declaring an events hook in the table cell options map if you'd be interested to take a look.

[knorrest]

Ok, I'll look at it - will get back to you when I've thought a bit...

[knorrest]

Ok, made a PR!

[knorrest]

One option for putting images in cells would be to add some code I now have in my app to the library:

`
(defn- h-align [alignment left width img-left]
(case alignment
:left left
:right (+ left (- width img-left))
(+ left (/ (- width img-left) 2))))

(defn- v-align [alignment bottom height img-height]
(case alignment
:bottom bottom
:top (+ bottom (- height img-height))
(+ bottom (/ (- height img-height) 2))))

(defn- fit-image-fn [halignment valignment ^URL img-url]
(fn [^Rectangle pos ^PdfContentByte canvas]
(let [left (.getLeft pos)
bottom (.getBottom pos)
width (.getWidth pos)
height (.getHeight pos)
img (Image/getInstance img-url)]
(.scaleToFit img width height)
(let [img-width (.getScaledWidth img)
img-height (.getScaledHeight img)
img-left (h-align halignment left width img-width)
img-bottom (v-align valignment bottom height img-height)]
(.setAbsolutePosition img img-left img-bottom)
(.addImage canvas img)))))`

Used like:

{:background-layer-fn (fit-image-fn :center :bottom trend-image)}

[yogthos]

Thanks, just saw the PR, and trying it out locally everything looks good to me. I think the helper functions would be useful to add. Might make sense to expose them declaratively via cell options. Maybe something like {:background-layer {:fit-image? true ...}.

[knorrest]

Ok, I’ll sketch something up and get back.

[yogthos]

Fantastic, and I'm good to do a release as soon as we get this ironed out.

[knorrest]

Thinking about it, maybe the best option is to just add a section in the readme with some examples. Theres a million things that one could do in cell event callbacks, with image background or overlay and shading being the ones that I needed now. A few simple examples might be enough to just show the idea. I agree that the declarative approach is really nice, but since we're using the more "advanced" part of the underlying API here it might make sense to just expose that in a nice way.

[yogthos]

I'm ok with that, if some common patterns emerge we can add declarative syntax to cover those via the standard API at a later point. I can push out a release tonight then.

[knorrest]

Ok, I'll add something to the doc and make a PR. If you want that in the release you'll have to wait until tomorrow, I'm a bit stuck with other things today.

[knorrest]

Found some time, and did a PR with example added to the readme. :-)

[knorrest]

...and a release would be terrific!

[yogthos]

Fantastic, thanks for adding the docs and I just pushed out 2.3.2 with the updates.