Changed background image in 2d JavaScript game, now getting "Image Decode" freezes - javascript

I've built a 2d JavaScript game using a single PNG image as my canvas background. It's 13500x7500px and 1.5MB in size. My game ran smoothly until I realized I needed an even bigger image, so I switched it out to a 17500x7500px and 2MB PNG file and am now getting freezing every animation loop.
My question is twofold - first, what is happening differently now than before? I didn't change anything other than the image. Is it some kind of caching issue?
And second, how can I stop the freezes from happening? I'm hoping I don't have to recode everything to incorporate an image splitter that pieces in smaller parts of the background as I move.
The thing is when I switch the original 13500x7500px image back into the program, it runs smoothly, even on different browsers. It's just with the bigger image I have an issue with.

Related

Showing a page content at once

I have a website which contains some images in index.php
The problem I am facing is the whole page is not loading at once, I think images are taking some time to load
So what I have done is, I am showing an loading image at first and then after some time I am showing the page, that resolves the problem. But I am curious to know is there any other better way to do this?
I prefer to optimise the hell out of my images.
PNG images
You can use pngcrush to optimise your PNG files for you, but personally I find that once I'm done with it pngcrush only succeeds in making it bigger.
Use Indexed-PNG wherever possible. This will limit you to 256 colours, and most graphics editors won't allow partial transparency in Indexed-PNG (but it is possible - you just need the right editor. I use a custom PHP script with the GD image library) but you can expect to drop file size down to just a tiny fraction of what it was.
Reduce the amount of colours overall. PNG compression works best with blocks of the same colour, so reducing the number of colours improves compression.
GIF images
Especially for animations, there's a lot of things you can do.
Reduce the number of frames. Avoid duplicate frames at all costs, and just set the previous frame to have a longer display time.
Use combine rather than replace if possible. You will again have problems with transparent areas, but by using combine you can have each subsequent frame only change the stuff that... changes. This avoids the redundancy of re-writing the entire image if only a small part changes. GIMP has a useful filter "Animation > Optimize for GIF" which will do this for you.
Reduce colours as much as possible. GIF is limited to 256 colours, but if you can limit yourself to 32 or so, you'll get a much smaller file.
Using the above techniques, I once managed to shove 8MB of raw image data into a 125kb animated GIF.
JPG images
JPG is great for photos, but cameras have a tendency to write MASSIVE files.
Play around with the compression factor. Start at around 40%, and slowly bring it up until it looks acceptable. GIMP will show you a preview and the resulting filesize, so make use of that to find an acceptable compromise.
Scale the image down. You don't need 9 megapixels or however massive resolution cameras take now...
The above should help you reduce the amount of size taken by your images. Obviously, you should also cache images appropriately, so they only need to be retrieved once. Also make sure that you specify width and height on image elements so that the browser can reserve the space for them and avoid jumping around as they load...
And you should be pretty good.
It's hard to say what other options are available without knowing what the page looks like, but one option is to reserve space for the images so that the page text renders quickly in the correct position, and the images then load later.

HTML5 cross-browser PNG sequence for 3D

I'm in the middle of creating a 3D video slot machine game in HTML5.
The game is great and it works perfectly in Firefox. It uses PNG sequences to give a 3D look to the characters within the game and the effects. The total amount of PNG's is 550 (70 per animation).
The main problem comes with Safari (Desktop, iPad and iPhone). When I load in the longer animations, which are over 100 PNG's, the framerate drops dramatically to around 4. I assume this is because of the Safari image memory not being able to hold 550 images well - despite it only totaling about 10mb.
Given that file size is also critical, as it's a web game, I considered swapping all the PNG's to GIF's in order to roughly half the size - However, before I embark on this journey, I figured the same thing would happen because of the number of images.
So the question here is - For a PNG sequence style game, what would be the best cross-browser compatible way of doing this in HTML5?
My only thought so far is to have a spritesheet per animation, placed into a div and moved on the left/top. Alternatively, could it be an issue with the way im preloading the images?
Unfortunately I'm unable to show any source code.

HTML large image performance problems

I'm trying to make a sick slider like this http://learnlakenona.com/
But I'm having major performance problems in chrome (it seems their site doesn't even run the slider on chrome). I'm displaying the images by using background-image CSS on divs, adding them as img tags caused even more lag.
I disabled all javascript and noticed I was still getting lag just with having some huge images sitting on top of eachother.
Here's just some images sitting there. Try changing the size of the panels, redrawing the images locks it up. (sometimes it runs okay for a bit, it's weird)
http://jsfiddle.net/LRynj/2/
Does anyone have an idea how I can get acceptable performance on a slider like this!? (images need to be pretty big)
Optimize your image assets by resizing them in an image editor or lowering the quality.
You can also use free tools online:
http://sixrevisions.com/tools/8-excellent-tools-for-optimizing-your-images/
The site uses HUGE transparent PNGs for a parallax effect, so:
you'll have to reduce the total weight of your images: you can try to convert these PNGs to PNG-8 if they aren't already. Quantizations algorithms and such do a very good job at reducing images to 256 colors without too much degradation of quality.
you've to keep transparency for the parallax effect. Both types of transparency are compatible with PNG-8: GIF-like opaque/tranparent bit of transparency on each pixel and "PNG-32"-like (PNG-24 + 8 bits of transparency) where each pixel has 256 levels of transparency. Adobe Fireworks is particularly good at creating such "PNG-8+alpha" images; converters also exist but they're not perfect (depends of your images).
loading the minimum part of your image that is seen immediately and only later the rest of your 9600px-wide (!) would greatly reduce the time to first view. You can achieve that by slicing your images by chunks of 1920 or 2560px, load the viewed part of the 3 images as background images and via a script that would execute only after the DOM is ready load all the other parts. Not too much parts because that would imply more assets to download but still not a 4MB sprite :) Bonus: by slicing your 3 images to PNG-8, each PNG will have its own 256-colors palette and overall quality will be better (not as perfect as a PNG-24 but better than a single 9600px PNG-8 that could only use 256 colors total. More shades of grey for the man suit in one PNG, more shiny colors for the ball-and-stick molecule, etc
EDIT: and don't ever try to load that on a smartphone! I do like Media Queries and avoid UA detection because it isn't needed most of the time and never perfect but that's one of the cases (choosing to load 8MB of images) where it'll be welcome... Ignoring users that don't have optic fiber and won't wait for your site to display is another issue not related to your question.

html5 canvas "graphics persistence" on reposition/resize

I noticed that when you move a canvas around or when you resize it, everything inside gets erased. I remember having a similar problem in windows forms applications in C#.
Anyway, what's the best way to keep the graphics on canvas, even after it moves etc.? (using javascript)
I've been working on a paint using canvas and websockets, you can see my problem here: http://students.info.uaic.ro/~tudor.berechet/ (just go to Coboards, select the Brush tool, click a bunch of times on canvas and then resize the window or enlarge the canvas)
One more thing I noticed, running the site off my HDD, this problem doesn't occur. which makes me wonder if there's some strange error somewhere.
I definitely need a persistent canvas, because I'm gonna have to implement the hand tool to move it around...
What say you?
The problem seems to have gone after cleaning up my code a bit. I still don't know what was causing it, but it seems that the canvas drawings now remain intact even after I move/resize the canvas.
Please confirm. [EDIT] confirmed.
The point is, my original assumption that canvas graphics are not persistent seems to have been wrong. There was most likely some coding error that was "erasing" my canvas.

JavaScript and draggable images - can I optimise it?

I'm working on a web application where we have a very large image (4000 * 2000 pixels) that can be dragged about the place, zoomed in/out.
When the image isn't zoomed in or out, it can be dragged about very fast and it looks great. As soon as i change the size of the image by some factor, the dragging becomes dreadfully slow.
I have just noticed that I have a height attribute on the image, but don't have a width attribute.
This behaviour is similar in both IE and Firefox, for obvious reasons, it works slightly faster in FireFox.
I have been looking at the GoogleMaps where they also have a very smooth draggable images.
What sort of optimisation I can do to achieve a similar result?
Thank you
Google Maps relies on lots of small, tiled images, as opposed to one large image. That way, they can be loaded in and out of memory, as you move around.
The simplest way to optimise the image would be to slice it up.
If you want to offer multiple levels of zoom, you may also want to consider rendering images at different levels as well, rather than relying on the browser to image process at run time.
Additionally, look at the image format you use! GIF and PNG offer compressed file-sizes over images such as JPEG and TIFF (although, obviously quality does take a hit).

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