StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

POC++, how to load images and count pixels of certain colours
primarykey
Id
3835712
data
AcceptedAnswerId
3835751
AnswerCount
4
ClosedDate
CommentCount
1
CommunityOwnedDate
CreationDate
2010-10-01T00:18:24.063
FavoriteCount
0
LastActivityDate
2010-10-04T06:17:44.350
LastEditDate
2017-05-23T12:18:38.430
LastEditorUserId
-1
OwnerUserId
431649
ParentId
0
PostTypeId
1
Score
0
ViewCount
1735
LastEditorDisplayName
text
Body
here's my problem: I'm looking for a way to import an image into C++ then traverse its pixels, incrementing a counter every time a pixel of a certain colour is found. I've done some research, but I haven't found anything particularly useful. <a href="http://openil.sourceforge.net/" rel="nofollow noreferrer" title="DevIL">DevIL</a> looks like a good option, but I'm not sure where to start. Here's a bit of C++/python pseudo-code hopefully illustrating what I'm trying to do: <pre><code>for image in folder: A = 0; B = 0; for pixel in image: if (pixel == colourA) {A++} if (pixel == colourB) {B++} //Output the count of colours for each image outputToFile(A, B); </code></pre> Does anyone have some tips on where to start? Thanks EDIT Some extra information: I'm using Windows 7 and all the images are .pngs EDIT2 I've got everything working, except actually finding out the colour of the current pixel. Currently I'm using this: <pre><code>int blue = ((uchar *)(img->imageData + pixelX*img->widthStep))[pixelY*img->nChannels + 0]; </code></pre> But it doesn't work, and I have no idea how it works. I haven't been able to find anything about this that I could understand. Could anyone point me in the right direction on how to find the RGB values of a certain pixel? Edit3 Done! For anyone who finds this trying to do a similar thing, most of my remaining questions and a fair bit of code can be found <a href="https://stackoverflow.com/questions/3851604/c-access-violation-using-opencv-to-get-rgb-value-of-pixel">here</a>. Thanks for the help!
Tags
<c++><image><devil>
Title
C++, how to load images and count pixels of certain colours
singulars
PostAcceptedAnswerId
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
PostParentId
1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. USCommunity
UserOwnerUserId
1. USJBenson
plurals
PostLinksPostIdRelatedPostId
1. PL
 singulars
 LinkTypeLinkTypeId
 LTLinked
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
2. PO
 singulars
 PostTypePostTypeId
 PTAnswer
3. PO
 singulars
 PostTypePostTypeId
 PTAnswer
VotesPostIdCreationDate
1. This table or related slice is empty.
CommentsPostId
1. COYou're trying to compute a (partial) histogram. Your average graphics library should be able to do this for you (imagemagick, at least).
 singulars
 PostPostId
 POC++, how to load images and count pixels of certain colours
 UserUserId
 USSeth

Querying!

Guidance

A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.