In Raphael you can load up images in the following manner:
var image_one=paper.image("some_url", x,y,width,height);
But the thing is that I am splicing the image, and I need several of those cuts, preferably without reloading the original image. That is because loading up only a single large image via http is faster than many small. Apparently there is some overhead in each upload that can become quite substantial.
But anyways, how can I make a copy of a Raphael image, after it has been loaded into ram?
I have already tried:
var image_two=image_one;
But it seems like that is only creating another link to the image.
This kind of internal copying is done via Raphael's .clone(), which is as simple as this:
var newElem = oldElem.clone();
Element.clone() works on elements including paths, images, rects, circles... but not sets.
Here's a simple demo - play around with splicing as desired.
http://jsbin.com/ufayuw/1/edit
If you want the clone to be hidden until it is needed, hide it with .hide()
Related
I'm working with fastai, trying to pass some images to a dataloader. The original images are kind of pinkish, but after passing them they appear mostly as green-black (see image in link below):
Original pinkish image (up) and example images (down) after passing them to dataloader, and the code.
The code I've used for the datablock and to show the images is:
example = DataBlock(
blocks=(ImageBlock, CategoryBlock),
get_items=get_image_files,
splitter=GrandparentSplitter(),
get_y=parent_label,
item_tfms=Resize(128)) #already tried it without item_tfms just in case, still black-green
dls = example.dataloaders(path)
dls.show_batch(nrows=1, ncols=3)
I tried with .tif and .jpeg images, and both show the same problem. The only thing that comes to my mind is that somewhat somewhere is not reading correctly the color format (RGB according to my original files), or maybe transforming it; but I'm not able to figure it out.
Just in case it's important, I'm working in a Jupyter notebook with a MackBook Air M1.
Thanks!
Irene
I'm trying to create a tool to rasterise vector images—stored in PDF files—on macOS, but the resulting images contain artifacts around the edges of some shapes. Preview.app, on the other hand, always renders the PDF flawlessly, as shown in this example:
I've tried:
Loading the PDF document using PDFKit, and rendering the page using both draw(with:to:) and thumbnail(of:for:)
Loading the PDF document into an NSImage (which creates an NSPDFImageRep), and using cgImage(forProposedRect:context:hints:)
In both cases I get these aliasing-like artifacts as seen on the left-hand-side of the image above. The PDF file is out of my control, so can't be changed to fix any issues it might have. I'm currently trying to migrate away from Cairo (which renders correctly) to Apple's PDF rendering for performance reasons (PDFKit renders it much more quickly, albeit with these artifacts).
Is there anything I've missed which would fix the output?
So it looks like the issue was caused due to me rasterising PDFs on multiple threads (specifically my tool rasterises PDFs in multiple resolutions, so I thought why not simultaneously).
Performing the operations sequentially on the main thread instead fixed it. I thought that I had come up with a way to use it concurrently by initialising the CGContext manually (instead of using NSImage's lockFocus()/unlockFocus() and NSGraphicsContext.current), but alas, as I soon as I add a context.scaleBy (to generate the images at different sizes), it fails again.
So for now I'm just doing it on the main thread until another solution comes along.
I'm making a silverlight website which includes paint-like features including freedraw. To achieve this I used the technique described on the following website: http://codeding.com/articles/freehand-drawing-in-silverlight .
The problem is, when I run the demo project it will start to lag extremely after just a few seconds of drawing. I realise that that is probably caused by the amount of shapes this techniue requires, however, and this is my main question:
How on earth does the demo on the website not lag nomatter howmuch I draw, while my local project which should have the EXACT same code lags right away?
I tried finding something about improving canvas performance overall, but the only thing I found was turning the drawing into a static image, which is not really ideal since I use undo/redo functionality.
The number of shapes added to the Canvas shouldn't be the reason for the lagging, there must be something else like converting the drawing into image for undo/redo functionality. For undo/redo, you can save the strokes-information instead of images. Creating & storing images during each undo/redo operation will consume too much memory.
A stroke is nothing but a set of points from the start (mousedown event) to end (mouseup event), and a set of strokes forms a complete drawing. You can always recreate the drawing using the saved strokes-information (just like you can recreate using images). You can use simple data-structures like List<List<Point>> to store a complete drawing, this is very memory efficient instead of creating & storing the image itself.
this is not a question about a specific programming problem, it's about examining different concepts. If the moderators don't feel this is ok, delete my question.
I need to display 100 png images in a table td, and the images are 75x16 PNGs. In order to reduce the number of HTTP requests, I grouped all 166 images (only roughly 100 are shown at one time) in a big spritesheet, and have used the IMG tag to display the output, one image at a time. This is the code:
CSS:
.sprites {background-image:url('folder/spritesheet.png');background-color:transparent;background-repeat:no-repeat;display:inline;}
#png3 {height:16px;width:75px;background-position:0px 0;}
#png5 {height:16px;width:75px;background-position:-75px 0;}
PHP:
$classy = "png" . $db_field['imageid'];
echo "<td>" , "<img src='transparent.gif' class='sprites' id='$classy' alt='alt' align='absmiddle'/>" , "</td>";
$classy is a variable which is calling the correct image based on the SQL query output. transparent.gif is a 1px transparent gif. And this is the result, images are shown correctly inside a table:
The page loading speed increased significantly, maybe 50-60%. In one of my earlier questions some concerns were raised over this being good practice or not. But it works.
The only other solution I've found is using jar compression, but that concept works for Firefox only. This is the code which is used for displaying these same images using jar compression (PHP, no CSS):
$logo = "jar:http://www.website.com/logos.jar!/" . $db_field['imageid'] . ".png";
echo "<tr>" , "<td>" , "<img src='$logo' alt='alt' width='75' height='16'/>";
All of the 166 images are compressed in a jar archive and uploaded to the server, and as jar is a non-solid archive, only the called image is extracted, not all of them. This solution is lighting fast and I've never seen a faster way of displaying that many images. The concept is here and deserves a link. Another advantage over CSS sprites is that with jar each image can be individually optimized for size (e.g one is optimized to 64 colors, another one to 128, 32...depending on the image) and a large spritesheet can not be optimized as it contains a lot of colors.
So, does anyone know of a solution which would be equally fast as jar? If using CSS sprites to display content is bad practice - what is good practice which gives the same result? The key here is the loading speed of the website with as few HTTP requests as possible.
Not really an expert on this but I had my share in these thing also
HTTP Requests
Ever heard of the "2 concurrent connections" (recent browsers have around 6-8). Loading a lot of stuff means if 2 are loading at the same time, the others have to wait in line. Loading it in one big chunk is better. This is the main reason why spriting is used. Aside from the connection limit, you manage those "same purpose" images in one image.
Cache
Now, one big chunk I say but you might ask "Does that make it even worse?". Nope, becasue I have an ace up my sleeve and that's where "cache" comes in to play. One page load is all you need, and then, poof! The rest of the pages that need that image are like the speed of light and Saves you from another HTTP request. Never underestimate the power of the cache.
Images
Other things you can do is to optimize your images. I have used Fireworks and I really love it's image optimization tools. To optimize, here are personal guidelines i follow which you can use in your situation:
GIFs for icons, JPGs for images, PNGs for transparent stuff.
remove unused colors. yes, you can do this in some tools. cuts down size
never resize images in the html. have resized versions instead.
lose quality. yes, there is such thing. lower your image quality to reasonable limits. losing it too much makes your image too "cloudy" or "blocky"
progressive loading images. What it does is it "fast-loads" a blurred image then clears it up later.
avoid animated images. they are a bloat, not to mention annoying.
Server Tricks
There are connection limits - but that does not prevent you from using other domains or even subdomains! Distribute your content to other domains or subdomains to increase the number your connections. For images, dedicate a subdomain or two for it, like say img1.mysite.com and img2.mysite.com or another domain mysite2.com. not only is it beneficial for your user, it's beneficial to distributing server load.
Another method is using a Content Delivery Network (CDN). CDN has a global network of servers, which contain "cached" versions of your website resources. Like say i'm in Asia, when i view your site with CDN'ed resources, it finds that resource in the server nearest Asia.
Mark-up
Not necessarily related speed and semantics but the use of id should be reserved for more important purposes. If you use ID to mark images for their styles, what if there was another element that needs the same image? IDs need to be unique, they can't be used twice. So i suggest using multiple classes instead.
also, IDs take precedence over classes. to avoid unexpected overrides, use classes. learn more about CSS specificity.
.sprites {
background-image:url('folder/spritesheet.png');
background-color:transparent;
background-repeat:no-repeat;
display:inline;
height:16px; /*same width and heights? place them here instead*/
width:75px;
}
.png3 {
height:16px; /* in cases you need a different dimension, this will override */
width:75px;
background-position:0px 0;
}
.png5 {
background-position:-75px 0;
}
$classy = "png" . $db_field['imageid'];
echo <img src='transparent.gif' class='sprites {$classy}' alt='alt' align='absmiddle'/>";
I embed small images/icons in the style sheet:
.someicon{
background-image:url('data:image/png;base64,iVBORw0KGg....');
}
this works with all modern browsers, and does not require me to create sprites (plus it even saves one additional file to load).
In development, the images are defined in the style sheet normally like so:
.someicon{
background-image:url('../images/someicon.png');
}
and I have a system that generates the final style sheet (including consolidating all CSS into one, minifying and replacing the image reference with the data: url) automatically whenever I make a change to a style sheet.
This works well and saves me a ton of work. When compressed with gzip, the CSS file is not much bigger than the individual files added together. After optimizing the PNG/JPG files, the CSS for my start page is 63K uncompressed. Even with a slightly smaller sprite file, I would probably not save more than a fraction of a second in load time for the average user, so I do not bother with sprites.
I would like to loop through a sequence of images. I have tried using a Pivot control, but I don't like the blank space in between image transitions. I would prefer to use something that will animate between images smoothly. I also looked at the LoopingSelector control, but I can't seem to set the orientation to horizontal.
I'm assuming you're interested in a kind of image viewer like iOS offers, swiping right or left to navigate through the photos. If that's the case, I hate to say it but i think you're looking at building your own control.
I think to implement it properly these are the essential things you need to think about and address:
For performance' sake, load all the images you have into memorystream objects and store the binary data (you can get creative with this and only store the first 10-15 images, depending on how large the images are, doing this would enable your control to support thousands of images and still perform like a champ).
Once an image is about to be on-screen set the source of the image to the saved memorystream object that has the bytes loaded into it (this will minimize the work that the UI thread does, keeping the control performant and responsive)
Use Manipulation events to track the delta x of the motion someone uses when swiping left to right in order to actually perform the moving of the items
Move the images by changing their Canvas.Left property (you can go negative I think, otherwise just make your canvas the width of all the images you have combined)
Look up some of the available libraries to support momentum so you can have a natural smooth transition between images