My app requires that each user has a profile picture of around 140*140px. Right now I am using jpgs, I am wondering if performance wise it will be better to use pngs. I read pngs are good for small UI elements and images, jpg for large images with detail such as photos. Obviously my profile pics are photos but they are small. Would it make much difference switching to png? Thanks
JPEG is best for small file sizes of photos, even for low resolutions.
PNG makes sense when there are many pixels of the exact same color next to each other. This is not the case with photos.
These should be helpful for you.
When to use PNG or JPG in iPhone development?
PNG vs. GIF vs. JPEG vs. SVG - When best to use?
Apple optimizes PNG images that are included in your iPhone app bundle. In fact, the iPhone uses a special encoding in which the color bytes are optimized for the hardware. XCode handles this special encoding for you when you build your project. So, you do see additional benefits to using PNG's on an iPhone other than their size consideration. For this reason it is definitely recommended to use PNG's for any images that appear as part of the interface (in a table view, labels, etc).
As for displaying a full screen image such as a photograph you may still reap benefits with PNG's since they are non-lossy and the visual quality should be better than a JPG not to mention resource usage with decoding the image. You may need to decrease the quality of your JPG's in order to see a real benefit in file size but then you are displaying non-optimal images.
File size is certainly a factor but there are other considerations at play as well when choosing an image format.
My app uses flat graphics, which mostly consists of lines and flat surfaces...
Whats the best approach for building the UI?
use PNG images as much as possible (like for the attached picture, the whole background would be an image)
use 4 UIViews (in this example case) with background color to make the background and the 3 lines
use CoreGraphics to actually draw in drawRect (or somewhere else?)?
subclass UIView and draw PDF content
any other approach?
What are the performance impacts? The advantage of the first two, is that they can be done in IB, but is there a downside (like performance or quality or caching)? I also heard of a trend of using CoreGraphics for drawing all the time...
So basically the fastest way is to use PNG files (stretchable and normal), also if you are using PNG files it will be easy to change the design and fix eventual bugs.
When you are using PNG files, try to reduce the size of the PNGs (stretchable images for backgrounds) for a better performance and a small size of the app.
CoreGraphics is more complex and can add strange bugs or performance problems if you don't know what you are doing, but can be use also for simple view styling.
On every project that I've done I couldn't use only one of these two because of the project complexity or because I was to lazy to open photoshop and add extract some designs.
As H2CO3 said is not that simple. Each format suits particular requirements, there are no written laws, I just ca tell you what I do.
Small pieces of UI, such as buttons, icons etc: I normally use PNG or PDF. You can subclass a UIView to draw PDF vector content. The plus with PDF is that if the source is a vector image, you could not take care about physical-logical points.
Images or Hi-res images, such as image of a content: In this case I use JPG, for they small size respect of PNG. They take little bit more to decompress but usually the size is very smaller compared to PNG.
In general PNG can use alpha, JPG no
Image is a big topic, nowadays I always try a way to find symmetry in UI elements and use stretchable UIImages with PNG.
For you example I will use PNG witch stretchable left and right side. Instead of use 640 px image, you can use 10 px image, with stretchable right margin and stretchable left margin.
[update]
It should be said that if you use stretchable images you will get a lot of performance boost, since the image will be smaller, you will occupy less memory on the "disk", less memory on the heap thatnks to the GPU stretching and less decompressing times
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I need to edit a png image,by giving it border and drop shadow effect. But the final size of the edited image is too high to use for a mobile app .I know that size of jpeg is less compared to that of png.So i convert that image to jpeg and tried to give drop shadow and border effect.But that image is not having transparent background..Is their any other methods to accomplish this using jpeg?
Another option is to try either ImageOptim for losseless compression, or its lossy cousin, ImageAlpha.
ImageOptim tries a series of lossless algorithms to shrink a PNG and selects the smallest result of the bunch. It has taken 25% to 50%+ of quite a few of our images.
ImageAlpha, on the other hand, is lossy and can further crunch the image, with results more like JPEG but without losing Alpha.
You would also do well to disable PNG compression in Xcode as shown here, with additional details here.
What #minitech wanted to say is not about scaling, it's about file compression. jpg and png files usually have some data that could be removed from the file. There are some compression methods to reduce file size (note that is size in kbs, not in scale measurement). Jpg images can reduce file size by reducing image quality, too.
If you want another file type that accepts transparency, there are the gif format, which gives you a smaller file, but have some drawbacks, like a lack of alpha channel (variable transparency). Check this link for more details: http://www.w3.org/QA/Tips/png-gif
There are a couple of online file compressors. If you want to compress png files, you could try using http://tinypng.org/
No, jpeg image wont support transparency.But you can change the white background coming along with jpeg image
I am able to use PNGs that have drop shadows but the effect when displayed on the BlackBerry looks like it collapses the transparent channel down from its original smooth gradient to only several transparent values giving it a choppy look.
The same issue is encountered by drawing on the UI using BlackBerry fields or the graphics.drawBitmap method. Anyone want to share hints for getting great looking transparent effects on the BlackBerry?
Dither your images or pre-composite them. When loading an image on a BlackBerry, you get at most 4 bits of alpha data, which allows 4 bits each for RGB. So, if you want to dither your transparent images, go for RGB4444. If you don't dither them, that's what causes 8-bit alpha to just be mapped to the nearest 4-bit value.
If you include no alpha data (i.e., precomposite), you can get RGB565, which will have a better image quality overall, but you will have to deal with static positioning for your dropshadows.
This question already has answers here:
What are the different usecases of PNG vs. GIF vs. JPEG vs. SVG? [closed]
(14 answers)
Closed 9 years ago.
I'm using ImageMagick to convert some files from one format to another. I was always under the impression that .png files were supposed to be as big/small as .jpg if not smaller, and definitely smaller than .gif.
However when I run
convert photo.jpg photo.png
The files I'm getting out is about 6 times bigger than the original jpg.
Original jpg is a regular photo about 300x500 px, 52 kb. Output is a proper png of the same dimensions, but size is about 307 kb?
Does anyoone know what the hack is going on? Am I doing something wrong?
P.S.:
I tried both on Debian and Windows with the same results.
P.P.S.:
Also when I add resize option to this and resize to 10000 x 10000. Converting and resizing to jpg takes a few seconds, but it works, if I do the same of png, I jsut strt running out of memory altogether
P.P.P.S.:
For people who keep marking this question as duplicate of PNG vs. GIF vs. JPEG vs. SVG - When best to use? . Please read carefully and understand the question. It's not a duplicate, since this question asks' about files produced programmatically with specific application (image magick). The question you marking as duplicate, is asking which image format is better to use on the web. Two DIFFERENT questions.
The key thing to note here is that each image file format is best for specific purposes.
JPEG stands for “Joint Photographic Experts Group.” That right there should tell you that the .JPG file format is optimized for photographs. It doesn’t work so well for line-art, logos, gradient or tiled / patterned backgrounds, and the like. .JPG’s DCT (Discreet Cosine Transform) artifacts (the “blocky” artifacts we all know and loathe) are much more noticeable with line art and logos than with photos.
PNG has replaced GIF for everything that GIF was ever good for, except one, and that only because no clear standard has emerged: animations. Animated .GIFs are well known on the Web. There are two competing standards for animated .PNGs: APNG and MNG.
APNG is supported in most modern browsers, and is also fully backwards compatible (the file extension is .PNG, not .APNG, and if any program that can display .PNGs but doesn’t know APNG is “fed” an APNG, it will display either a stand-in image of the developer’s choice, or the first frame of the animation if no such stand-in was provided — as far as the older program is concerned, it’s just an ordinary single-frame .PNG with that one image in it — the rest is safely ignored). Gecko (FF, etc.) and Presto (Opera) support it natively, and Google Chrome (using Webkit) can with an add-on.
MNG has the backing of the actual PNG-format development team, but is its own format and is not backwards compatible, but is more powerful and flexible. Right now, only KHTML-based browsers (Konquerer) support it: not Trident (IE), Gecko, Webkit (Chrome, Chromium, Safari), nor Presto.
PNG does everything (except animations unless enhanced with APNG) that GIF does, and better. All else being equal, a .PNG will almost always be smaller than a .GIF at the same resolution and bit depth. Like .GIF, .PNG can support color depths up to 8 bits per pixel in indexed-color (paletted) mode, but unlike .GIF (yet like .JPEG) it also supports direct-color mode at 24 bits per pixel.
In either mode it can add 8 bits of alpha transparency, unlike .GIF (which can only do indexed color transparency [pick a color out of the palette to be replaced with 100% transparency, aka invisibility] — .PNG can do that, too). Alpha transparency produces much better results than indexed transparency, because the pixels can be partially transparent, whereas with indexed transparency (the only kind available in .GIF) your choices are either opaque or invisible. This makes for “halos” around non-rectangular objects when placed against background colors other than the one the .GIF or indexed .PNG was originally “matted” against. It also inhibits being able to do effects such as glows, drop shadows, and, of course, see-through colored objects (without dithering). Alpha transparency can do all of those things with ease, against almost any background (glows would be largely invisible on a white background, and drop shadows would be invisible on black, but you know what I mean).
Yes, you can do 8-bit alpha transparency in an indexed-color .PNG! And guess what? Even Microsoft Internet Explorer 6 can display those just fine, complete with transparency! It’s only the 32-bit .PNGs (24-bit RGB color + 8-bit alpha) that IE6 choked on and displayed as gray!
The most well-known program that can export PNG8 (indexed color) with alpha transparency is Adobe (formerly Macromedia) Fireworks. The Photoshop “Save for Web and Devices” (at least as of CS3) could not do that, despite having basically lifted the feature from Fireworks when Adobe bought out Macromedia. It can save PNG8, but only with indexed-color transparency.
Anyway, full 32-bit (or even 24-bit) PNGs will be pretty large, though usually much smaller than the nearest equivalent .BMP or .TGA or uncompressed .TIFF or some such (unless you’re trying to do a photograph with it — that’s what JPEG is for!). It will usually be somewhat smaller even than .RLE (losslessly compressed .BMP) or losslessly compressed .TIF, all else being equal.
Unlike most of these other formats, PNG also supports 48-bit RGB color, with optional 16 bits of alpha transparency, for extremely high quality (much higher than most monitors can display). These are best used as an intermediate storage format, to retain information from a high bit depth scanner or camera (RAW mode) or some such. Their file sizes would be quite large, despite the lossless compression.
One thing that .PNG cannot currently do is handle non-RGB color spaces such as CMYK or L*a*b.
In short:
For photographs, use .JPG.
For line art and logos of limited color, use indexed-color .PNG (PNG8), with alpha transparency if needed.
For line art and logos of extensive color (e.g. lots of gradient fills, metallic chrome-type reflection effects, etc.), use direct-color .PNG (PNG24) with alpha if needed, if you want the best quality or need transparency (and don’t mind it not working in IE6 or use one of a variety of IE6 workarounds for transparent PNGs), and don’t mind the larger files and bandwidth usage. Otherwise, use .JPG, but be aware that the quality will be degraded. You may need to crank the JPEG quality up pretty high, especially for logos or other graphics with “text” in them, which would reduce your file size savings.
For non-Flash/Silverlight/video/HTML5 Canvas animations, .GIF if the main choice at present, but be prepared to switch to APNG (I don’t think MNG is going to beat it, despite the more official support from the JPEG developers).
JPG is a lossy compression algorithm while PNG is a lossless one.
This fact alone will (in general) make JPG images smaller than PNG ones. You can tweak the compression ratios for each format, so it could also be that you're not compressing your PNG files as much as your JPG ones.
For a photographic image saving as JPG will usually produce a smaller file than PNG as there's more noise or randomness in the image for the compression to work with. Images created by graphic art tools will tend to have more hard edges and areas of solid colour which will compress better in PNG.
If you have text in your image then PNG is going to produce a better quality image as the harder edges of the characters won't be blurred like they would be if JPG is used.
GIF is smaller because it's based on an colour palette (of 256 colours) rather than the separate RGB values for each pixel (or group of pixels) in JPG and PNG.
The PNG format can provide images of 24 bits per pixel or 8 bits per pixel. JPG is a 24 bit format, but it uses lossy compression to reduce the file size significantly. PNG and GIF both use lossless compression, but GIF only works with 8 bits so it requires your image to have 256 colors or less - this often results in a grainier picture.
Try the -colors and -dither options in ImageMagick to reduce the number of bits in your PNG output. At that point it should be comparable to the GIF file size. If you need to reduce it further, there are utilities to optimize the PNG.
The .jpeg file format is a lossy format, it throws information away. Which makes for good compression ratios. The .gif file format is not lossy but loses other information, it only supports 256 colors. The .png file format is not lossy and preserves the color range.
It depends on the kind of image. JPEG's lossy compression works very well on images with lots of color gradients (i.e. photos).
Try it on an image consisting of areas with the same color separated by sharp edges (screenshots are good, unless they show a photo desktop background, and the fancy window borders and task bar of Vista and Windows 7 also tend to mess this up). JPEG is bad at that kind of thing, and you'll probably find PNG to compress better (probably better than GIF too).
Replying to :
Does anyone know what the hack is going on? Am I doing something wrong?
yeah I study this, you aren't doing nothing wrong, you produced 8-bit/color RGB PNG
I solve it with reduce or compress png with pngnq ( http://pngnq.sourceforge.net/ ) that produce 8-bit/color colormap PNG.
pngnq seems to me the most improved project, since is a fork of others like pngquant etc, and is normally in main stream of Linux distros so I just do this:
convert photo.jpg png:- | pngnq -s 1 > photo.png
For the last upvoter (2016): pngnq as been deprecated in favor of pngquant (https://github.com/pornel/pngquant)