I have an rgb image data in the first 3 channels of a uchar4 array. Is there a function that I can utilize in CUDA libraries in order to save this uchar4 format as an RGB image, or is there another way for saving RGB images in CUDA?
Saving RGB image data to a file does not involve CUDA. You use CUDA to process your data in whichever way you desire.
Once that is done and you have achieved a result, copy your RGB data back to the host and save it. You can basically pick whatever your favorite routine/library is to save RGB data to a file. Boost.GIL as recommended by Roger Dahl does seem to be a nice option indeed.
As such, there is no particular functionality within CUDA that allows you to save your image data to a file.
Related
I'm trying to use low-level functions (fopen and fread) to read a grayscale image of type uint16 in TIFF format as follows:
fid = fopen(filepath,'r');
img = fread(fid,[ncolms, nrows], 'uint16=>uint16')';
The obtained image matrix is different from that obtained by simply using imread:
img = imread(filepath);
The resulting images are shown below (the left is by fread and the right is by imread):
In addition to the obvious intensity difference, one may also note that fread image has some artifacts in the top edge of image. I think this must be due to their different mechanisms of reading images.
I want to know how to use such low-level functions as fopen and fread to read images (grayscale, not binary), equivalently to using imread, if they can.
Those "artifacts" you're seeing are likely the header and tag data stored in the file before the image data. I would suggest taking a look at this TIFF File Format Summary. It will tell you exactly how to read all this extra information, if you really want to do it yourself. Note that some of this extra tag information (i.e. ImageHeight, ImageWidth, BitsPerSample, SamplesPerPixel, etc.) will be useful in determining exactly how to read the image data correctly, and thus match the image you get from the imread function.
I used these codes to produce an RGB image with gray levels between 50 and 170.
a='C:\Users\sepideh\Desktop\IP_abadpour\S45C-113050518040.jpg';
b=imread(a);
b=b+50;
b(b>170)=170;
and you'll see when I call functions max and min, it is proved that the gray levels are between 50 and 170.
max(max(max(b)))
ans =
170
min(min(min(b)))
ans =
50
then I used imshow and imsave functions to save the image with the name "50to170"
c=imshow(b);
d=imsave(c);
Now I read the written image in this way:
a='C:\Users\sepideh\Desktop\IP_abadpour\50to170.jpg';
b=imread(a);
This time when I call max and min functions,I see:
max(max(max(b)))
ans =
235
min(min(min(b)))
ans =
16
I mean it seems that gray levels have been changed after using imshow and imsave functions!
Why does it happen?
Is it because of the format (.jpg) that I'm using when employing imsave function?
Instead of using imsave, use imwrite
b=imread(a);
b=b+50;
b(b>170)=170;
imwrite(b,'50to170.png','png')
Notice that I am saving it as a png file instead of a jpg to prevent compression. Bitmap also saves it without compression.
This method is a more direct way to save raw image matrices than using imshow and imsave.
If you want the same functionality of imsave (selecting where the file goes) check out "uiputfile" to get file name and location.
I tested it.
1.First of all you can't use imsave(b) because the function imsave expects its first input argument to be a valid handle to a single graphics object.So first you should show the image in form c=imshow(b) and then use c as an input for function imsave.
2.If you want to save the image without showing it first use function "imwrite" and pass b as the first input argument to it.
Note that if you don't want gray levels be changed after saving, you should use 'bmp' as the save format not 'jpg'.
Because 'jpg' does not support indexed images and "imwrite" converts indexed images to RGB before writing data to JPEG files so the gray levels might be changed.It's not related to the contrast stretching when showing the image in matlab.It's related to the format used to save the image.
I have read pixel values of an raster image using GDAL libraries in visual studio 2010(vc++).
Next is , I have to crop the image (subset) according to the grid given in shape file.
Forget about the grid this time.
I just want to clip square or rectangular area and save to new file.
I have read some documents which suggest about gdal_translate and gdal_warp function to use but it can only be run in python where as i want to use c++.
Please help me as early as possible.
I have solved the problem of cropping the image using VC++ with gdal libraries. I have created VRTDataset of my desired size of raster to be cropped and then save it using CreateCopy().
I have some raw data in a file that I would like to store in an image file (bmp, jpg, png, or even gif (eegad)). I would like this to be a two way process: I need to be able to reliably convert the image file back later and get a file that is identical to the original file.
I am not looking for a how-to on steganography; the image file will probably be one pixel wide and millions of pixels high and look like garbage. That is fine.
I looked into the Imagemagick utility convert, but am intimidated by the large number of options and terse man page. I am guessing I could just use this to convert from a 'raw' black channel to png, but would have to specify a bunch of other stuff. Any hints? I would prefer to work within Imagemagick or using Linux utilities.
If you are wondering, there's nothing black hat or cloak and dagger about my request. I simply want to automatically backup some important data to a photo-sharing site.
I'd plow into ImageMagick if that's what you'd prefer anyway.
Specific image formats support storing text data to different degrees, and ImageMagick supports all of the formats you mentioned. I'd choose the one that lets you store what you need.
Is it possible to create a raw image in Fortran? I was thinking BMP but not really sure what extension would be best.
Basically, I want to be able to have an array or a text file that contains the color values for each pixel, so a 3 pixel wide red image would just be FF0000FF0000FF0000 or something similar to that
You could use the PPM format. http://en.wikipedia.org/wiki/Netpbm_format
Aspect 1: you have to know the format of the image file. Then you write that format. Likely any standard image files (PPM, BPM, TIFF,...) will include some sort of header. This is inherent in writing a standard image file, independent of the language.
Aspect 2: Fortran 2 used to be relentlessly record oriented, even for unformated (binary) files, which didn't "play" nicely with files written by other languages such as C, or file formats specified without the record deliminators expected by Fortran. But the new Stream I/O method produces non-record files. An image file will be unformatted (binary), so in the open statement include:
access='stream', form='unformatted', ....
Yes, you can create a PNG using our gtk-fortran binding (GNU GPL v3) which includes interfaces to the GdkPixbuf library. A pixbuf is a 1D array containing the RGB intensities of each pixel of the image.
Note that it is possible to just use the GdkPixbuf library (~20 lines of code), without building a GTK gui:
https://fortran-lang.discourse.group/t/making-computer-graphics-in-fortran-without-gui-just-creating-a-png/70
https://github.com/vmagnin/gtk-fortran/wiki
You just need a Fortran compiler (Fortran >=2003).