I'd like to alter images programmatically. Specifically for the iPhone, but, general answers could help. For example, how could I, programmatically, add filters effects, such as those available in Photoshop.
Clearly it is possible as exemplified by apps such as Fat Booth. What is the starting point for this? Load an image as NSData and learn how PNGs are encoded and go to work with the algorithm? Possible? Easier solutions?
Thanks for the help!
Chapter 21 of iPhone SDK Development has an example of how to display and manipulate a photo that is pretty easy to follow. More complex effects require more complex code, but it's something to start with.
First obtain image in raw format (raw like in raw bytes for every pixel [rgb][rgb]) then manipulate the pixels and convert back from raw format to image.
Here you can find information how to convert uiimage to and from raw pixels data, for example:
Raw to UIImage: Creating UIImage from raw RGBA data
UIimage to Raw: Can I edit the pixels of the UIImage's property CGImage
If you need geometric transformations you can use mapping of coordinates or opengl and use your image as a texture on some mesh, manipulate the mesh (geometrically) and render the scene back to an image.
You don't need to know how the images are encoded into PNGs or JPGs it can be done for you by the system. You just need to know what you want to achieve and then build your own algorithm.
Have fun!
Related
I have a raw data image which is potentially sparse and has continuous coordinates (e.g. 1000 pixels which are positioned on a spiral, the coordinates are floats). What is the best way to load this data into ITK for further processing and the ability to save the image in physical coordinates?
My research so far: There is itk::SpecialCoordinatesImage which I could inherit to override TransformPhysicalPointToContinuousIndex(…) and TransformPhysicalPointToIndex(…). I do not know the position and pixel number before reading the hole data stream. So for a minimal amount of speed I will need to resort the data "manually". Isn't there a better way?
I am more familiar with vtk than itk, so propably what comes into my mind is a bit biased. You could:
load the raw data into a vtk unstructured grid (see for example the function ReadFinancialData in http://vtk.org/gitweb?p=VTK.git;a=blob;f=Examples/Modelling/Cxx/finance.cxx )
then voxelize it to an image. For example. see http://www.vtkjournal.org/browse/publication/713 (I've never used it, I dont' know if it is compatible with the last versions) or http://www.vtk.org/Wiki/VTK/Examples/Cxx/PolyData/PolyDataContourToImageData
I have extracted the depth map of 2 images and stored them as .tif file
now I would like to use openGL to join these two images depending on their depth
so I want to read the depth for each image from the .tif file and then use that depth to draw the pixel with the higher depth
to make it more clear the depth map are two images like this
link
so say I have the pervious image and I want to join it with this image
link
my question is how to read this depth from the .tif file
Ok, I'll have a go ;-)
I see the images are just grayscale, so if the "depth" information is just the intensity of the pixel, "joining" them may be just a matter of adding the pixels. This is generally referred to as "blending", but I don't know what else you could mean.
So, you need to;
Read the 2 images into memory
For each pixel (assuming both images the same size):
read the intensity from image A[row,col]
read the intensity from image B[row,col]
write max(A[row,col],B[row,col]) to C[row,col]
Save image C - this is your new "joined" image.
Now OpenGL doesn't have any built-in support for loading/saving images, so you'll need to find a 3rd party library, like FreeImage or similar.
So, that's a lot of work. I wonder if you really want an OpenGL solution or are just assuming OpenGL would be good for graphics work. If the algorithm above is really what you want, you could do it in something like C# in a matter of minutes. It has built-in support for loading (some formats) of image file, and accessing pixels using the Bitmap class. And since your created this images yourself, you may not be bound the the TIFF format.
I'm trying to use OpenCV to read/write images for me. Currently, I have them in a different, non-standard format, and I know how to get them into OpenCV's containers. Here are the requirements:
The pixels are 1, or 3 bands, U8, U16, U32, or F32
The images have metadata, random stuff, like the camera ID that took the images. I would like the metadata to be vi/notepad editable
I want to write as little code as possible when it comes to low level stuff. My experience is that this stuff requires the most maintenance.
I can define the format. It's only to read and write for these programs.
I don't want the pixels to be anything but binary, '0.5873499082' is way too much data for one float.
Is there a way to describe to OpenCV how to read and write image types it doesn't know? Are there image types already available for the types of images I have?
My interim solution is to use boost to serialize the image, and save the metadata in a separate file.
Try using gdal library for reading images and then convert it to IplImage.
OpenCV can't do that for you, you can store the metadata in a separate file, or you can use for example the jpeg exif (that won't be notepad editable though).
I'm building a program to convert an image file (whatever file type would be easiest) to G-Code for use on a rep-rap with a pen plotter attachment.
I'm wondering if i wanted to process the image pixel by pixel and check things like pixel color, how could I do this with C++?
I would really like to know how I can process a bitmap image, pixel by pixel, to check the color of the pixel.
The best way is to use a library, like for example Magick++.
When you load an image, you can access it's pixels data with Blob
You will probably want to use an existing library that has been tested.
But for fun/practice/etc, this would be a good exercise and wouldn't be impossible to do. The Bitmap Format is (relatively) simple compared with other image formats. The Wikipedia page has some tons of info, including some C++ code. It looks like once you've gotten past the header information, you get to a pixel array that shouldn't be difficult to parse.
Good luck.
Most image formats consist of a header and the actual raw image data. A bimpap image is no different. If you don't want to use one of the existing libraries, or if you are not allowed to, you should read about bitmap format :
http://en.wikipedia.org/wiki/BMP_file_format
Once you understand this you could create appropriate structs/classes to store the information you want from the header such as x,y size, bpp etc. And also have a pointer to the raw image data. You could then simpy iterate through every pixel and do whatever you want with it :)
Once you decipher the image file, I suggest you place the pixels into a matrix, for the first pass. (Future revisions can use other methods to access the pixels).
You can apply transformations to the pixels by using matrix multiplication. You can also access the pixels individually by using array indexing.
Search the web and SO for "introduction to graphics c++".
I'll first tell you the problem and then I'll tell you my solution.
Problem: I have a blank white PNG image approximately 900x900 pixels. I want to copy circles 30x30 pixels in size, which are essentially circles with a different colour. There are 8 different circles, and placed on the image depending on data values which I've created elsewhere.
Solution: I've used ImageMagicK, it's suppose to be good for general purpose image editing etc. I created a blank image
Image.outimage("900x900","white");
I upload all other small 30x30 pixel images with 'read' function.
I upload the data and extract vales.
I place the small 'circle' images on the blank one using the composite command.
outimage.composite("some file.png",pixelx,pixely,InCompositeOp);
This all works fine and the images come up the way I want them too.
However its painfully SLOW. It takes 20 seconds to do one image, and I have 1000 of them. Surely there must be a better way to do this. I've seen other researchers simulate images way more complex and way faster. It's quite possible I took the wrong approach. Maybe I sould be 'drawing' circles instead of 'pasting' them or something. I'm quite baffled. Any input is appreciated.
I suspect that you just need some library that is capable of drawing circles on bitmap and saving that bitmap as png.
For example my Graphin library: http://code.google.com/p/graphin/
Or some such. With Graphin you can also draw one PNG on surface of another as in your case.
You did not give any information about the platform you are using (only "C++"), so if you are looking for a platform independent solution, the CImg library might be worth a try.
http://cimg.sourceforge.net/
By the way, did you try drawing the circles using the ImageMagick C++ API Magick++ instead of "composing" them? I cannot believe that it is that slow.