Smooth (mouse) scroll for inline images?

Question

I display images in-line with begin_src & result blocks.

However, for large-images, when I scroll past the bottom of the image, I get a 'jerk' and the whole image is scrolled away. Similarly if I scroll up and run into an image, I get a jerk and see the whole image instead of seeing it incrementally bit by bit.

This makes it hard to work with large plantuml/graphviz diagrams in org-mode.

I would like a smooth scoll experience, to gently scroll past the image like in a web browser, without jerking.

I have tried:

(setq auto-window-vscroll nil)

and also

(setq scroll-margin 1
scroll-conservatively 0
scroll-up-aggressively 0.01
scroll-down-aggressively 0.01)

I tried smooth-scroll package and this snippet also.

However, it seems an in-line image only takes up 'one-line' and fixing emacs to scroll only by 'one-line' doesn't fix the issue.

Any solution to this issue?

[edit] Keyboard vs Mouse scrolling:

Mouse scrolling is implied. But keyboard scrolling would be a bonus if proper mouse scrolling would work.

[edit]
Somewhat of a workaround, but useful for working with images in org-mode was to open them in an external app that auto-reloads on file change. Example would be eog (eye of gnome) or shutter or prievew (on OS X). It can be configured via org-file-apps by adding:

extension: \.png\'
Command:   eog "%s"

Answer 1

Since Emacs 26.1, the buffer can be scrolled by individual pixels instead of just lines which can be used to smoothly scroll over images using the mouse wheel. To achieve this I have used the following configuration:

;;; Scrolling.
;; Good speed and allow scrolling through large images (pixel-scroll).
;; Note: Scroll lags when point must be moved but increasing the number
;;       of lines that point moves in pixel-scroll.el ruins large image
;;       scrolling. So unfortunately I think we'll just have to live with
;;       this.
(pixel-scroll-mode)
(setq pixel-dead-time 0) ; Never go back to the old scrolling behaviour.
(setq pixel-resolution-fine-flag t) ; Scroll by number of pixels instead of lines (t = frame-char-height pixels).
(setq mouse-wheel-scroll-amount '(1)) ; Distance in pixel-resolution to scroll each mouse wheel event.
(setq mouse-wheel-progressive-speed nil) ; Progressive speed is too fast for me.

Edit:

I have found that this solution has a few caveats that might be helpful to know:

• Scrolling over an image higher than the window will still cause the big jarring jump which sees the window scroll until the image is no longer visible (the next line is on the top of the window).
• You can't make the scrolling instant (less intensive) but yet still scroll by pixels rather than lines.
• When a new scroll event is issued before the existing animation is finished, the window jumps to the start of the next animation causing a discontinuity in the smooth scrolling.
• Many people have experienced such a performance degradation using this method that it is just simply not usable. Apparently this is common when some mode line modifications are used.

Answer 2

How about this:

;; scroll one line at a time (less "jumpy" than defaults)
(setq mouse-wheel-scroll-amount '(1 ((shift) . 1))) ;; one line at a time
(setq mouse-wheel-progressive-speed nil) ;; don't accelerate scrolling
(setq mouse-wheel-follow-mouse 't) ;; scroll window under mouse
(setq scroll-step 1) ;; keyboard scroll one line at a time

Answer 3

The problem as I understand it is that the image is a single line. Changing how scrolling behaves won't solve the problem.

The only solution I am aware of is to slice the image up so that there are technically many shorter images. This can be done using insert-sliced-image.

Answer 4

Below setting works extremely good:

https://www.emacswiki.org/emacs/SmoothScrolling

(setq pixel-scroll-precision-large-scroll-height 40.0)