I ve an image which has 6 images within it..I ve the task of cropping the 6 images out of this image..
Currently I follow this procedure..
1. Save copy of original image
2. Crop the image to get first image using any tool(Picasa)
3. Save the cropped image as image 1
4. Open the original to crop for image 2
5. Repeat this 6 times
Is there a way in which I can extract out all the 6 images in one go? Multi-cropping?
Yes, it's possible. You need to get familiarized with the ROI (Region of Interest) concept.
This C example shows how to set a ROI in an image. Basically it sets a ROI in a frame from the camera, creates a new image from it, does some processing (invert colors) in the image and then copies the image back to the original frame for display.
This Python example also shows how to work with ROIs.
From the OP description, it sounds like the OP just wants to automated way to crop an image into 6 pieces.
Google for "irfanview batch crop" or "ImageMagick batch crop"
If a more complex cropping logic/procedure is needed, then gfx library of the OP's language of choice should have a cropping function that they can code.
OpenCV would be an overkill for this task.
if OP insist on using OpenCV, then set the ROI
Mat image = imread("src_image_path");
Rect roi = Rect(x, y, w, h);
Mat image_roi = image(roi);
imwrite("dest_image_path", image_roi);
Related
In my rails app, i let the user upload images to use as thumbnails for resources they've made. I do all the image processing with imagemagick's convert command: i convert to jpg, letterbox it to 800x600px and then make some smaller thumbnail versions of that.
This is all working fine. The problem is that some images that have come off my iPhone, for example, have the wrong orientation. My desktop seems to variously deal with this: when i see the tiny thumbnail for the image in the file chooser dialog, it's got the wrong orientation, but if I open it in the image viewing tool, it's got the correct orientation.
Presumably there's some header or metadata or something in the image file which tells the app that it needs to rotate the file? I think that I need to read this in before I do any other processing of the image, so that I can rotate the image (if necessary) before doing all the other stuff.
Can anyone tell me how I can do this, in bash on an Ubuntu server?
thanks, Max
EDIT: a bit of googling suggests that this is to to with EXIF headers...
It's true that you will have to look for orientation value reading Exif metadata of Image. Using imagemagick you can get this value by
identify -format '%[exif:orientation]' <Path to Image>
//or by using
identify -format '%[orientation]' <Path to Image>
Exif Orientation values range from 1 to 8 and maps to orientation as below:
1 = Horizontal (normal)
2 = Mirror horizontal
3 = Rotate 180
4 = Mirror vertical
5 = Mirror horizontal and rotate 270 CW
6 = Rotate 90 CW
7 = Mirror horizontal and rotate 90 CW
8 = Rotate 270 CW
Thus, image would require orientation correction if this metadata tag returns with a non 1 value. If this tag returns with no value it can be assumed to be having normal orientation.
To correct orientation to normal you can use following command
convert -auto-orient <inputImagePath> <outputImagePath>
Try
identify -format "%f %[EXIF:Orientation]" <imagename>
This gives a number from 1 to 8. These numbers are documented here
I would like to be able to use the cpselect matlab tool (or a similar one) with the capability of showing both images (moving image and reference image) in RGB (I only managed to see moving image in RGB and reference image in grayscale).
Could someone point me to an alternative for this tool that would support this or anyway to be able to display both image in rgb in cpselect?
Thanks in advance.
Not sure what you're talking about, and I'm quite confused about your statement. cpselect is image independent. You can show both of them as colour or grayscale or one or the other. The example you're probably looking at is the one that comes with MATLAB: http://www.mathworks.com/help/images/ref/cpselect.html . One image is grayscale, while the other has a pinkish hue.
Here's an example showing both the source and target image as being in colour. I used onion.png that is a colour image that is part of the MATLAB system path:
im = imread('onion.png');
im_rotate = imrotate(im, 35);
cpselect(im, im_rotate);
We get:
I have grayscale satellite image which is processed from spectral data (band classifications). If i use jet colormap in imshow it will show absolute colormapped image. But if i try to imwrite in particular place it is saved like a bluish image. I saw one example in matlab central, but i didnt get. can anyone help me to write my image with colorscaled image.
Matlab central link: http://www.mathworks.in/matlabcentral/answers/25026-saving-grayscale-image-as-it-appears-in-jet-colormap-of-imagesc
there accepted answer link is : http://www.mathworks.com/matlabcentral/fileexchange/7943
I have tried many times, this will show colormaped images in plots (imshow) they didnt write anywhere with colormaped. Now i want to write my image with colormaped.
example code:
I= imread('image path');
imshow(I,'colormap',jet);
imwrite(I,'path','jpg'); /not working
or
imwrite(I,jet,'path','jpg'); /not working
Please help to solve this issue.
When you use imshow the colormap is always adjusted to the range of values in your image. imwrite however assumes your image has a value range of [0,1] if you are using single or double data types. Try to scale your image to the range [0,1] before saving.
If you provide a colormap in the call to imwrite, MATLAB assumes you are using an indexed image. Thus you will have to convert the image to the indexed format first. The following snippet worked for a test image I of mine:
% scale to [0,1]
I = I - min(I(:));
I = I ./ max(I(:));
% Create indexed image
[J,~] = gray2ind(I);
% Save image
imwrite(J,jet,'path','jpg');
Solution by hbaderts worked well for me, but later I found out that some images were still scaled slightly different way from imshow.
However, I might found a reason of an original problem. Just after Matlab starts, its default colormaps (including 'jet') are set to 64 colors (64x3). Then, if any image is shown with a colormap, for example if imshow('cameraman.tif'), colormap('jet') is executed, all default colormaps become 256x3 (can be verified with jetMap=jet; before and after). Then it might happen that an image was written with a colormap different from the one applied to image figure (for example, if a figure called after imwrite).
Finally I found this solution (no image pre-scaling needed):
% Create indexed image, explicitly using 256 colors
imInd=gray2ind(im,256);
% Convert indexed image to RGB using 256-colors jet map
jetRGB=ind2rgb(imInd,jet(256));
% Save image
imwrite(jetRGB,'jet.png');
The images I used have the same color scale now, both the saved one and the one shown in figure.
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().
Recently I downloaded paint.net. It can rotate images in every angle.
I need 360 images, each rotated different angle, with appropriate filename (1.jpg, 2.jpg etc).
The problem is- on paint.net I must rotate it 360 times manually which would take me forever.
Is there any sort of enviroment to rotate images the way I want?
I need this because I want to load the 360 images into a game in c++ and thats how I will rotate the images.
If you do it for a game, why wouldn't you write your own program that does it for you? Its the simpliest way.
For example check this simple python script:
# Make sure to install PIL after your regular python package is installed
import Image
image = Image.open("yourpicture.jpg")
for (a in range(360)):
image2 = image.rotate(a)
image2.save(str(a) + "jpg")
del image2
There's no such a tool in paint.net, but you can try writing your own plugin (check CodeLab plugin).