this question might be an "Open Question" and many of you might be eager to close it, but please don't. Let me explain.
As we all know, JPEG has two kinds of compression (at least in Photoshop save dialog)
optimized, where image was loaded kinda like line-by-line
progressive, where image was loaded first mosaic-like, the progressively better till the original resolution
I have read a lot of PNG/JPEG optimization articles before, but now I encountered this awesome third kind compression, from a wild random Google Image search. The JPEG in question is this
http://storage.googleapis.com/marc-pres/boston-event-1012/images/google-data-center.jpg
Try load the link in Chrome/Firefox (in IE/Safari only until the image was fully loaded then displayed)
you can observe:
image were loaded first in black & white
then looks like the Red channel loaded
next the Green channel loaded
last the Blue channel loaded
I tried loading it again with a emulated very slow connection, and observed that the JPEG is not only loads by channel order, but in progressive way as well. So first loaded image is blank-and-white mosaic then green-ish mosaic then gradually full color mosaic and finally full resolution and full color image.
This is amazing technology, suppose you are building an e-magazine, where each page has a lot of pictures, you want the user to fast flip browsing through pages, and this kind of image is exactly what works best. For fast preview, load blank-n-white thumbnail, if the user stays, fully load the original image.
So my question is: How could I generate such image using Python Pillow or ImageMagick, or any kind of open source software?
If you think this question is inappropriate please comment, don't just close it.
Update 1:
It turns out Google used this technology in all of its JPEG pictures 1, 2 e.g. this
Update 2: I found another clue
The image data in a JPEG file can be sliced up in many different ways, and the slices (or "scans" as they're usually called) can be stored in the file in many different orders.
In most JPEG files, the first scan in the file contains all of the image's color components, interleaved together if it is a color image. In a non-progressive JPEG, the file will contain just that one scan. In a progressive JPEG, other scans will follow, each of which may contain one component or multiple components.
But there's nothing that requires it to be done that way. If the first scan in the file does not contain all the color components, we might call such a file "non-interleaved".
Your examples files are non-interleaved, and they are also progressive. Progressive non-interleaved JPEGs seem to be more widely supported than non-progressive non-interleaved JPEGs.
The standard IJG libjpeg software is capable of creating non-interleaved files. Though it's not exactly easy, you can use its cjpeg utility, with the -scans option documented in the wizard.txt file.
Related
I'm trying to extract some a data (a map image) from a PNG file which is tiled somehow. The file itself is only 256x256 pixels (according to 'get info' on the mac) but is is 23MB. It is from an iPad app called Mud Map and it contains a map that I purchased but I've lost the original that I converted to this format. When I view this file (renamed to a .PNG) I see one section of the map - 256x256px.
I'm asking this question on StackOverflow because I want to know more about these tiled images. How does one create a tiled PNG and what is the software that will open and or create these things. I'm interested in what metadata is required too. I'm loving the outdoors and mapping!!
The answer to this question, is that it cannot be done in manner I have described.
The images in the PNG are not tiled, the the files are just merged together which is no doubt an individual feature of the program as is it does not appear to be any kind of standard.
I have no access to application you mentioned in IPad. Just share some thought about possible situation here.
1) Map tiles are commonly used in GIS web application such as Google maps and so on. It is used to improve the performance especially when user pan very often. A map displayed typical map window is divided into for instance 4*4 separate calls. So maybe only 4 call will be made when user just pan a little bit instead of get the whole map for the 16 tiles.
The source image for this tiles can be in pre-generated tiles or just one static map.
2) Assemble separate images to one in GIS is called image mosaic function. GIS server can read a collection of images and mosaiced them into one with the overlapping part handle based on a certain rule. And the images are in pre defined grid format which are seamless and no overlapping, then it is called tiled images. We could pre-generated the tiles from one mosaiced image, or we can server it on the fly. Some GIS server/library/application does have the tile server function built in.
I'm trying to do image comparison to detect changes in a video processing application. These are two images that look identical to me, but are different according to both
http://pdiff.sourceforge.net/
and http://www.itec.uni-klu.ac.at/lire/nightly/api/net/semanticmetadata/lire/imageanalysis/LireFeature.html
Can anyone explain the difference? Eventually I need to find a library that can detect differences that doesn't have any false positives.
The two images are different.
I used GIMP (open source) to stack the two images one on top of the other and do a difference for the top layer. It showed a very faint black image, i.e. very little difference. I then used Curve to raise the tones and it revealed that what seem to be JPEG artifacts, even though the files given are PNG. I recommend GIMP and sometimes I use it instead of Photoshop.
Using GIMP to do a blink comparison between layers at 400% view, I would guess that the first image is closer to the original. The second may be saved copy of the first or from the original but saved at a lower quality setting.
It seems that the metadata has been stripped off both images (haven't done a definitive look), so no clues there.
There was a program called Unique Filer that I used for years. It is tunable and rather good. But any comparator is likely to generate a number of false positives if you tune it well enough to make sure it doesn't miss duplicates. If you only want to catch images that are very similar like this pair, then you can tune it very tightly. It is old and may not work on Windows 7 or later.
I would like to find good image checkers / comparators too. I've considered writing my own program.
I am hiding a text file in an image using http://github.com/anirudhsama it works fine and I could able to extract the text file again back with my program.
But when I programmatically share the image in facebook, twitter and email, that shared image is not decode properly so I'm not getting the file back.
I retrive the image as follows:
UIImage *finalImageWithStegno = [UIImage imageWithContentsOfFile:fileName];
What I suspect is image compression when it is uploaded to the site. A simple way to check this is to hide a message in a cover image (obtain stego image). Upload the image on a website and download it. Compare the original stego image to the downloaded image. If they differ (byte by byte), there's your problem.
From a quick look at the code, it seems the app hides the data in the spatial domain, which is not robust. Your message is directly hidden in the image pixels and if they change (due to lossy compression, blurring, etc), your message will be lost. A solution to this would be to hide the data in the frequency domain. Another solution could be uploading the images with a filetype which doesn't get compressed? I don't know much how sites deal with images so the second suggestion may be impossible.
In any case, if uploading to a site distorts the image, look around for another app which may serve you unless you can code yourself. Then we can get into the specifics. :)
Your algorithm is not robust. Use Transform domain Stegnography to retain the information when its is re encoded. You may choose to embed in DCT coefficients or DWT Coefficients for better robustness.
I am creating a kind of 'map' in my app. This is basically only viewing an image with an imageView/scrollView. However, the image is huge. Like 20,000x15,000 px or something. How can I tile this image so that it fits? When the app tiles by itself, it uses way too much memory, and I want this to be done before the app I launched, and just include the tiled, not the original image. Can photoshop do this?
I have not done a complete search for this yet, as I am away, and typing on an iPhone with limited network connection..
Apple has a project called PhotoScroller. It supports panning and zooming of large images. However, it does this by pre-tiling the images - if you look in the project you will see hundreds of tiles for various zoom sizes. The project however does NOT come with any kind of tiling utility.
So what some people have done is create algorithms or code that anyone can use to create these tiles. I support an open source project PhotoScrollerNetwork that allows people to download huge jpegs from the network, tile them, then display them as PhotoScroller does, and while doing research for this I found several people who had posted tiling software.
I googled "PhotoScroller tiling utility" and got lots of hits, including one here on SO
CATiledLayer is one way to do it and of course the best if you can pre-tile the images downloading them from the internet (pay attention on how many connection you are going to open) or embedding them(increasing overall app size), the other is memory map the image on the file system (but an image with that res could take about 1GB), take a look at this question it could be an intersteing topic SO question about low memory scenario
I was trying to convert a GIF image (Ajax waiting like):
to AVI that will be used with TAnimate control (win32 animation control).
I have tried a few tools, but the problem is that the output AVI is either not suitable for the Animation control or not transparent.
Notes:
I don't use windows XP Themes manifest (D5).
the Common Avi's are transparent even if my program is not themed.
Using the GIF itself to show animation is not an option.
Do you know any tool that can help me with this conversion?
EDIT:
I have tried using ImageMagic with ffmpeg as described here. but I can't seem to set ffmpeg to encode to msrle.
Jasc Animation Shop is able to directly read an animated GIF and write out a compressed AVI. This is an old program that appears to be no longer offered by Corel (who acquired Jasc), but you may still be able to find the free trial version for example.
You could try the TGIFImage component (written for Delphi 5), which claims not only to support Animated GIFs, but also Transparency, as well as a means of converting a GIF to an AVI (and vice-versa).
Whether it does all that or not I cannot say as I haven't personally tested it. Like TLama mentioned in the OP comments above, I use my own means of playing each frame in an animated fashion (only mine uses a RES file and a TImage, where each frame is stored as a PNG for full semi-transparency support).
Many commercial tools do this conversion, including Corel Photo Paint, and others. A free trial is available for Corel Photo Paint, which comes included in the Corel Draw package. (Warning: It's huge, and expensive.) I don't think the transparency will be solved any more by corel photo paint's conversion than by anybody else.
Typing some words into Google, also reveals that DSPack from ProgDigy might help you.
The last time I did this, I abandoned the attempt to convert GIF transparency into AVI-with-transparency, because no AVI-encoding tool that I could find would preserve transparency. Thus the solution of leaving it as a gif, and putting a new control into your app (as LaKraven suggests) may be superior in the end, to fighting it.
I would suggest using GDIPlus native image renderer which can easily handle animated GIFs as well as many other image types, including multi-frame TIFFs (no MNG so far). I was able to find an example component which animates TImage instance:
http://www.progdigy.com/forums/viewtopic.php?p=13156
Please note I am aware that you are looking for a solution to AVI transparency, this is just an alternative way of presenting user with a "progress", which seems to be more lightweight (no dependency on windows media playback facilities) and flexible (such animation controller can be used on any image).