I have a top nav header bar I want to have about 40% opacity...
I was looking at other threads comparing .PNG vs css Opacity... from what I read, the .png might perform better...
so my question is...
for a top nav header: width:100%, height:50px;
Would it be better to use a 1x1 pixel transparent image, or something more like a 1x50 transparent image?
do thousands of 1x1 images load faster then several hundred 1x50 images?
nit picky i know...
thx
One single image will load much faster than many hundred larger images, but then you're going to waste an awwful lot of cpu time tiling/stretching that one single pixel.
What are you trying to achieve with the background? A gradient?
Related
I want to make a kind of slideshow based on scrolling the webpage.
My problem is that I have an image width of 78720x1015px in png-format.
The width of the image is determined by one single image of 1920px which is 41 times arranged next to each other. - It should be like a cartoon where an image moves by 100% (margin: -100%) and generates a feeling of a movie.
However, this results in an image width of 1920px x 41pics = 78720px.
This is of an enormous width, but what I am wondering about is that the filesize is only 975kB which is in my opinion not that big!? - However, somehow it takes a very long time to load the picture in the Webbrowser and the image is not of such quality as in my ImageViewer on Desktop.
Question 1: What do I have to consider when dealing with such a big image-width? What are the limits?
Question 2: Is there a better way make such kind of a slideshow? - Consider that the sliding itself shouldn't be visible. It should be like a movie based on about 40 pictures.
Thanks in advance!
PNG compresses very well, especially if it's a cartoon like you say that may use only a limited number of colours.
However, when loaded into memory, the device must load all that pixel data into RAM to display it. That's almost 80 million pixels in your case, which would be around 320Mb of uncompressed data. This is probably why the browser is struggling, and especially so if you're using margin to move it around as that requires a full re-draw of the image.
You may have better results with transform, as this should use hardware acceleration and also avoids the reflow part of a redraw since transforms don't affect page layout.
But the better solution would be to break it down into individual images. Have your code load in the next image, scroll it across, then load the next while scrolling and unload the one that's now off-screen to provide a relatively seamless view.
I am trying to create a background image on a webpage, which is similar to the 404 page used on tumbler...
http://testing404image.tumblr.com/
Here we can see a PNG which is 1623*1064 pixels, yet appears reasonably smooth gradient wise.
The direct link for the image is
http://testing404image.tumblr.com/images/status_bg.png?2
When I try to create a similar PNG (different colors, but same size) in Photoshop CS4 for Mac, the resulting file ends up at > 400k, whereas tumblers is 90k
Ive tried playing with all Photoshop options, including reducing number of colors to 55, but I cannot get the image below ~240k.
Ive also tried various optimising tools such as ImageOptim (http://imageoptim.com/) but to no avail.
Are there any properties of this PNG which result in a such a low file size?
I tried using JPG, thinking its better suited to gradient images, but even a 100% quality JPG resulted in noticeable aliasing, which an identical content/size PNG didnt have.
Thanks for any advice
Hi there changed the colours with
Image > Adjustments > Hue/Saturation - In Photoshop CS4
and this is the result:
as you can see it's almost the same size (75k).
Try playing around under the
Image > Adjustments
to get the color you are looking for and save as png with NONE for interlace.
Photoshop is not very good with PNG: I simply opened and saved it with the humble xnView (maximum compression), and got 74K. You can also convert it to paletted-image, and do some extra little tuning - PNGoptim gives me a final size of 64.548. I would't expect anything much better than that, the image is just too big.
BTW, be aware that using a gradient that is so big and so smooth that it a digital image (with 8 bits per pixel) cannot represent it without some banding. That image is really oversampled (you could resample it at 25% or less and display it scaled, and the result would be basically the same)
The actual reason is the source image your looking to have a lower gradient quality than the one you are making.
Just uncheck the Dither option (from the top toolbar in Photoshop) when filling the gradient color. the quality and smoothness of the gradient is decreased and therefore you get a very smaller file sized PNG output.
I have an application that let's users view images. The user decides what images to use, so the size can range from 10x10 to 10000000x10000000 (I am exeggerating). All is well up to a certain size, when the image is bigger than the iPhone's memory. Quite understandably.
But how do I fix it? Is there a way to load only a portion of the image (I'm using an CATiledLayer, so I could load/release tile by tile).
Thanks in advance!
Unless you have an uncompressed image format it would be very hard to load the image in patches, you will have to provide the patches that the user would load, determine what portion of the image to show, and load the correct patches. There is an example for this "ScrollViewSuite" that demonstrate that technique. But this technique does require a preprocessing step.
I have a png image file that is partly opaque and partly transparent. I display it in a UIImageView as a mask of sorts over another UIImageView layered behind it (as a sibling subview of a common superview). It gives me perfect borders around something painted using a finger on the lower UIImageView in my stack of UIImageViews. Perhaps there are better ways to do this, but I am new-ish, and this is the best way I came up with thus far. None the less, my app is in the App Store and now I want to enhance it to provide more images to use as the mask of sorts over the finger painting. But I don't want to bloat my bundle size by adding more static mask images as I did for the initial implementation. Not to mention I don't want to spend lots of time in photoshop making 100 masks. I'd rather programmatically change the color of the mask, without affecting the clear portion in the middle, which is not a simple regtangle or circle, but rather a complex shape. So my question is this: How can I change the colored portion of my loaded image without affecting the clear color portion in the middle? Is there a reasonably easy way to do this? Essentially I want to do what is described in this post (How would I tint an image programmatically on the iPhone?) without affecting the clear portion of my image. Thanks for any insights.
Have a look at the Tinted Image sample project. Try out the different modes until you get the effect you want.
I'm writing a card game for the iPhone, and I'm not sure about the best strategy for displaying the cards. I have a basic prototype that creates a UIImageView that can be dragged for each card with a dummy image. I wanted to use one large UIImage that contains the faces of all of the cards, and then have each draggable UIImageView display a part of that image. I must be misunderstanding what setBounds is for - I thought that controlled which part of the underlying image is displayed. So, two questions:
Is this the right approach?
How do I display just a part of the image?
Depending on your resolution, this might not be the best approach.
From Apple:
You should avoid creating UIImage
objects that are greater than 1024 x
1024 in size. Besides the large amount
of memory such an image would consume,
you may run into problems when using
the image as a texture in OpenGL ES or
when drawing the image to a view or
layer. This size restriction does not
apply if you are performing code-based
manipulations, such as resizing an
image larger than 1024 x 1024 pixels
by drawing it to a bitmap-backed
graphics context. In fact, you may
need to resize an image in this manner
(or break it into several smaller
images) in order to draw it to one of
your views.
Now, you are talking about breaking it up into several smaller pieces, but given UIIMage's caching, I am not sure what happens to memory every time you access the image and copy a sub-rect out of it. I think the approach I would take is to have an array of images, instead of one big one.