Add primitive use-image to use image by natural size

[yasuo-ozu]

Add the primitives:

use-image-by-natural-size : image -> inline-cmd

This is implementation of #296

[na4zagin3]

Just my two cents. Why not add a primitive that gets the soze (e.g., get-image-size : image -> (length * length)) instead?

[gfngfn]

Thank you for the development!

It also looks more preferable to me to provide get-image-size as na4zagin3-san suggests than to add use-image-by-natural-size. This is because use-image-by-natural-size can be easily implemented by using get-image-size (and use-image-by-width) but the opposite seems more complex; get-image-size would be thereby a more “primitive” operation.

[yasuo-ozu]

Thanks for replaying.

From my standings, I want to replace use-image-by-width with use-image-by-natural-size (= use-image), because use-image-by-width too respects image width (than height) so I think it is irrational. So use-image seems more primitive than use-image-by-width.

Using use-image and existing commands, the following commands can defined:

let get-image-size img =
    let ib = use-image img in
    let (w, h, d) = get-natural-metrics ib in
    (w, h)
let use-image-by-width img wid =
    let ib = use-image img in
    let (w, h, d) = get-natural-metrics ib in
    let hgt = h *' (wid /' w) in
    inline-graphics wid hgt 0pt (fun (x, y) -> (
        let g = draw-text (x, y) ib in
        linear-transform-graphics g
    ))

[yasuo-ozu]

To be short:
既存のuse-image-by-width はwidthを特別扱いしているのであまり合理的でなく、今のSATySFiではlinear-transform-graphicsが使えるのだから、use-imageをprimitiveにしてuse-image-by-widthはライブラリ定義にしたほうが良いのでは？という意見です。

違う例としては

get-initial-context : length -> [math] inline-cmd -> context

があるわけですが、これにおけるlengthは画像におけるlengthとは意味が異なる(文書のcolumnの幅)ので違和感はないです。

(ただこれはあくまで1意見であり、get-image-sizeの方が良さそうであればuse-image-by-natural-sizeを消してget-image-sizeを追加しようとおもいます)

[yasuo-ozu]

I updated the implementation to come up with the following ideas:

• Add primitive use-image (called use-image-by-natural-size in upstream discussion) to import image by its natural size.
• Delete use-image-by-width from vminst.ml and re-implemented it in pervasives.satyh, which is no longer primitive, just a library definition.

Key point is:
I think, use-image is more primitive than use-image-by-width

Is there any comments on this idea?
Thanks a lot.

[yasuo-ozu]

以下のアイデアを実現するために実装を更新しました。

• 画像を「自然なサイズ」で使用するuse-imageプリミティブ(上のdiscussionでuse-image-by-widthと呼んでいたもの)を実装した。
• use-image-by-widthをvminst.mlから削除し、ライブラリ定義としてpervasives.satyhに再実装した。

キーポイントは
私は思う, use-imageはuse-image-by-widthよりもprimitiveであると。