I am using MATLAB in my office and Octave when I am at home. Although they are very similar, I was trying to do something I would expected to be very easy and obvious, but found it really annoying. I can't find out how to import TIFF images in Octave. I know the MATLAB geotiffread function is not present, but I thought there would be another method.
I could also skip importing them, as I can work with the imread function in some cases, but then the second problem would be that I can't find a way to write a georeferenced TIFF file (in MATLAB I normally call geotiffwrite with geotiffinfo inputs inside). My TIFF files are usually 8 bit unsigned integer or 32 bit signed integer. I hope someone can suggest a way to solve this problem. I also saw this thread but did not understand if it is possible to use the code proposed by Ashish in Octave.
You may want to look at the mapping library in Octave.
You can also use the raster functions to work with GeoTiffs
Example:
pkg load mapping
filename=”C:\\sl\SDK\\DTED\\n45_w122_1arc_v2.tif”
rasterinfo (filename)
rasterdraw (filename)
The short answer is you can't do it in Octave out of the box. But this is not because it is impossible to do it. It is simply because no one has yet bothered to implement it. As a piece of free software, Octave has the features that its users are willing to spend time or money implementing.
About writing of signed 32-bit images
As of version 3.8.1, Octave uses either GraphicsMagick or ImageMagick to handle the reading and writing of images. This introduces some problems. The number 1 is that your precision is limited to how you built GraphicsMagick (its quantum-depth option). In addition, you can only write unsigned integers. Hopefully this will change in the future but since not many users require it, it's been this way until now.
Dealing with geotiff
Provided you know C++, you can write this functions yourself. This shouldn't be too hard since there is already libgeotiff, a C library for it. You would only need to write a wrapper as an Octave oct function (of course, if you don't know C or C++, then this "only" becomes a lot of work).
Here is the example oct file code which needs to be compiled. I have taken reference of https://gerasimosmichalitsianos.wordpress.com/2018/01/08/178/
#include <octave/oct.h>
#include "iostream"
#include "fstream"
#include "string"
#include "cstdlib"
#include <cstdio>
#include "gdal_priv.h"
#include "cpl_conv.h"
#include "limits.h"
#include "stdlib.h"
using namespace std;
typedef std::string String;
DEFUN_DLD (test1, args, , "write geotiff")
{
NDArray maindata = args(0).array_value ();
const dim_vector dims = maindata.dims ();
int i,j,nrows,ncols;
nrows=dims(0);
ncols=dims(1);
//octave_stdout << maindata(i,0);
NDArray transform1 = args(1).array_value ();
double* transform = (double*) CPLMalloc(sizeof(double)*6);
float* rowBuff = (float*) CPLMalloc(sizeof(float)*ncols);
//GDT_Float32 *rowBuff = CPLMalloc(sizeof(GDT_Float32)*ncols);
String tiffname;
tiffname = "nameoftiff2.tif";
cout<<"The transformation matrix is";
for (i=0; i<6; i++)
{
transform[i]=transform1(i);
cout<<transform[i]<<" ";
}
GDALAllRegister();
CPLPushErrorHandler(CPLQuietErrorHandler);
GDALDataset *geotiffDataset;
GDALDriver *driverGeotiff;
GDALRasterBand *geotiffBand;
OGRSpatialReference oSRS;
char **papszOptions = NULL;
char *pszWKT = NULL;
oSRS.SetWellKnownGeogCS( "WGS84" );
oSRS.exportToWkt( &pszWKT );
driverGeotiff = GetGDALDriverManager()->GetDriverByName("GTiff");
geotiffDataset = (GDALDataset *) driverGeotiff->Create(tiffname.c_str(),ncols,nrows,1,GDT_Float32,NULL);
geotiffDataset->SetGeoTransform(transform);
geotiffDataset->SetProjection(pszWKT);
//CPLFree( pszSRS_WKT );
cout<<" \n Number of rows and columns in array are: \n";
cout<<nrows<<" "<<ncols<<"\n";
for (i=0; i<nrows; i++)
{
for (j=0; j <ncols; j++)
rowBuff[j]=maindata(i,j);
//cout<<rowBuff[0]<<"\n";
geotiffDataset->GetRasterBand(1)->RasterIO(GF_Write,0,i,ncols,1,rowBuff,ncols,1,GDT_Float32,0,0);
}
GDALClose(geotiffDataset) ;
CPLFree(transform);
CPLFree(rowBuff);
CPLFree(pszWKT);
GDALDestroyDriverManager();
return octave_value_list();
}
it can be compiled and run using following
mkoctfile -lgdal test1.cc
aa=rand(50,53);
b=[60,1,0,40,0,-1];
test1(aa,b);
Related
TL;DR;
How to get the macro name used for size of a constant size array declaration, from a callExpr -> arg_0 -> DeclRefExpr.
Detailed Problem statement:
Recently I started working on a challenge which requires source to source transformation tool for modifying
specific function calls with an additional argument. Reasearching about the ways i can acheive introduced me
to this amazing toolset Clang. I've been learning how to use different tools provided in libtooling to
acheive my goal. But now i'm stuck at a problem, seek your help here.
Considere the below program (dummy of my sources), my goal is to rewrite all calls to strcpy
function with a safe version of strcpy_s and add an additional parameter in the new function call
i.e - destination pointer maximum size. so, for the below program my refactored call would be like
strcpy_s(inStr, STR_MAX, argv[1]);
I wrote a RecursiveVisitor class and inspecting all function calls in VisitCallExpr method, to get max size
of the dest arg i'm getting VarDecl of the first agrument and trying to get the size (ConstArrayType). Since
the source file is already preprocessed i'm seeing 2049 as the size, but what i need is the macro STR_MAX in
this case. how can i get that?
(Creating replacements with this info and using RefactoringTool replacing them afterwards)
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define STR_MAX 2049
int main(int argc, char **argv){
char inStr[STR_MAX];
if(argc>1){
//Clang tool required to transaform the below call into strncpy_s(inStr, STR_MAX, argv[1], strlen(argv[1]));
strcpy(inStr, argv[1]);
} else {
printf("\n not enough args");
return -1;
}
printf("got [%s]", inStr);
return 0;
}
As you noticed correctly, the source code is already preprocessed and it has all the macros expanded. Thus, the AST will simply have an integer expression as the size of array.
A little bit of information on source locations
NOTE: you can skip it and proceed straight to the solution below
The information about expanded macros is contained in source locations of AST nodes and usually can be retrieved using Lexer (Clang's lexer and preprocessor are very tightly connected and can be even considered one entity). It's a bare minimum and not very obvious to work with, but it is what it is.
As you are looking for a way to get the original macro name for a replacement, you only need to get the spelling (i.e. the way it was written in the original source code) and you don't need to carry much about macro definitions, function-style macros and their arguments, etc.
Clang has two types of different locations: SourceLocation and CharSourceLocation. The first one can be found pretty much everywhere through the AST. It refers to a position in terms of tokens. This explains why begin and end positions can be somewhat counterintuitive:
// clang::DeclRefExpr
//
// ┌─ begin location
foo(VeryLongButDescriptiveVariableName);
// └─ end location
// clang::BinaryOperator
//
// ┌─ begin location
int Result = LHS + RHS;
// └─ end location
As you can see, this type of source location points to the beginning of the corresponding token. CharSourceLocation on the other hand, points directly to the characters.
So, in order to get the original text of the expression, we need to convert SourceLocation's to CharSourceLocation's and get the corresponding text from the source.
The solution
I've modified your example to show other cases of macro expansions as well:
#define STR_MAX 2049
#define BAR(X) X
int main() {
char inStrDef[STR_MAX];
char inStrFunc[BAR(2049)];
char inStrFuncNested[BAR(BAR(STR_MAX))];
}
The following code:
// clang::VarDecl *VD;
// clang::ASTContext *Context;
auto &SM = Context->getSourceManager();
auto &LO = Context->getLangOpts();
auto DeclarationType = VD->getTypeSourceInfo()->getTypeLoc();
if (auto ArrayType = DeclarationType.getAs<ConstantArrayTypeLoc>()) {
auto *Size = ArrayType.getSizeExpr();
auto CharRange = Lexer::getAsCharRange(Size->getSourceRange(), SM, LO);
// Lexer gets text for [start, end) and we want him to grab the end as well
CharRange.setEnd(CharRange.getEnd().getLocWithOffset(1));
auto StringRep = Lexer::getSourceText(CharRange, SM, LO);
llvm::errs() << StringRep << "\n";
}
produces this output for the snippet:
STR_MAX
BAR(2049)
BAR(BAR(STR_MAX))
I hope this information is helpful. Happy hacking with Clang!
I am writing a pre-processor for Free-Pascal (Course Work) using m4. I was reading the thread at stackoverflow here and from there reached a blog which essentially shows the basic usage of m4 for pre-processing for C. The blogger uses a testing C file test.c.m4 like this:
#include
define(`DEF', `3')
int main(int argc, char *argv[]) {
printf("%d\n", DEF);
return 0;
}
and generates processed C file like this using m4, which is fine.
$ m4 test.c.m4 > test.c
$ cat test.c
#include <stdio.h>
int main(int argc, char *argv[]) {
printf("%dn", 3);
return 0;
}
My doubts are:
1. The programmer will write the code where the line
define(`DEF', `3')
would be
#define DEF 3
then who converts this line to the above line? We can use tool like sed or awk to do the same but then what is the use of m4. The thing that m4 does can be implemented using sed also.
It would be very helpful if someone can tell me how to convert the programmer's code into a file that can be used by m4.
2. I had another issue using m4. The comment in languages like C are removed before pre-processing so can this be done using m4? For this I was looking for commands in m4 by which I can replace the comments using regex and I found regexp(), but it requires the string to be replaced as argument which is not available in this case. So how to achieve this?
Sorry if this is a naive question. I read the documentation of m4 but could not find a solution.
m4 is the tool that will convert DEF to 3 in this case. It is true that sed or awk could serve the same purpose for this simple case but m4 is a much more powerful tool because it a) allows macros to be parameterized, b) includes conditionals, c) allows macros to be redefined through the input file, and much more. For example, one could write (in the file for.pas.m4, inspired by ratfor):
define(`LOOP',`for $1 := 1 to $2 do
begin')dnl
define(`ENDLOOP',`end')dnl
LOOP(i,10)
WriteLn(i);
ENDLOOP;
... which produces the following output ready for the Pascal compiler when processed by m4 for.pas.m4:
for i := 1 to 10 do
begin
WriteLn(i);
end;
Removing general Pascal comments using m4 would not be possible but creating a macro to include a comment that will be deleted by `m4' in processing is straightforward:
define(`NOTE',`dnl')dnl
NOTE(`This is a comment')
x := 3;
... produces:
x := 3;
Frequently-used macros that are to be expanded by m4 can be put in a common file that can be included at the start of any Pascal file that uses them, making it unnecessary to define all the required macros in every Pascal file. See include (file) in the m4 manual.
I'm trying to write data structures defines in C to my Arduino Uno board's non-volatile memory, so the values of the struct will be retained after the power goes off or it is reset.
To my understanding, the only way to do this (while the sketch is running) would be to write to arduino's EEPROM. Although I can write individual bytes (sets a byte with value 1 at address 0):
eeprom_write_byte(0,1);
I am stuck trying to write a whole struct:
typedef struct NewProject_Sequence {
NewProject_SequenceId sequenceId;
NewProject_SequenceLength maxRange;
NewProject_SequenceLength minRange;
NewProject_SequenceLength seqLength;
NewProject_SceneId sceneList[5];
} NewProject_Sequence;
Because of the EEPROM's limit of 100,000 writes, I don't want to write to the Arduino in a loop going through each byte, for this will probably use it up pretty fast. Does anyone know a more efficient way of doing this, either with EEPROM or if there's a way to write to PROGMEM while the sketch is running? (without using the Arduino Library, just C).
RESOLVED
I ended up writing two custom functions -- eepromWrite and eepromRead. They are listed below:
void eepromRead(uint16_t addr, void* output, uint16_t length) {
uint8_t* src;
uint8_t* dst;
src = (uint8_t*)addr;
dst = (uint8_t*)output;
for (uint16_t i = 0; i < length; i++) {
*dst++ = eeprom_read_byte(src++);
}
}
void eepromWrite(uint16_t addr, void* input, uint16_t length) {
uint8_t* src;
uint8_t* dst;
src = (uint8_t*)input;
dst = (uint8_t*)addr;
for (uint16_t i = 0; i < length; i++) {
eeprom_write_byte(dst++, *src++);
}
}
The would be implemented like this:
uint16_t currentAddress;
struct {
uint16_t x;
uint16_t y;
} data;
struct {
} output;
uint16_t input
eepromWrite(currentAddress, data, sizeof(data);
eepromRead(currentAddress, output, sizeof(data));
Several solutions and or combinations.
setup a timer event to store the values periodically, rather then
back to back.
use a checksum, then increment the initial offset,
when writing. Where when reading you attempt each increment until
you have a valid checksum. this spreads your data across the entire
range increasing your life. modern flash drives do this.
Catch the unit turning off, by using an external Brown Out Detector to trigger an INT to then quickly write the EEPROM. Where you can then also use the internal BOD to prevent corruption, before it falls below safe writing voltages. By having the external significantly higher than the internal thresholds. The time to write before complete shutdown can be increased by increasing the VCC capacitance. Where the external BOD is compared before the VCC and not directly the VCC itself.
Here is a video explaining how to enable the internal BOD, for a ATtiny, where it is nearly identical for the other ATmega's. Video
The Arduino EEPROM library provides get/put functions that are able to read and write structs...
Link to EEPROM.put(...)
The write is made only when a byte has changed.
So, using put/get is the solution to your problem.
I'm using these in a wide (25k) project without any problem.
And as already said I've used a timer to write not each time but some time to times.
Turning off detection is also a very good way to do this.
I am using C and need a stream buffer mechanism that I can write arbitrary bytes two and read bytes from. I would prefer something that is platform independent (or that can at least run on osx and linux). Is anyone aware of any permissive lightweight libraries or code than I can drop in?
I've used buffers within libevent and I may end up going that route, but it seems overkill to have libevent as a dependency when I don't do any sort of event based io.
If you don't mind depending on C++ and possibly some bits of STL, you can use std::stringstream. It shouldn't be too difficult to write a thin C wrapper around it.
Is setbuf(3) (and its aliases) the 'mechanism' you are searching for?
Please consider the following example:
#include <stdio.h>
int main()
{
char buf[256];
setbuffer(stderr, buf, 256);
fprintf(stderr, "Error: no more oxygen.\n");
buf[1] = 'R';
buf[2] = 'R';
buf[3] = 'O';
buf[4] = 'R';
fflush(stderr);
}
I am trying to emulate grep pattern of UNIX using a C program( just for learning ). The code that i have written is giving me a run time error..
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#define MAXLENGTH 1000
char userBuf[MAXLENGTH];
int main ( int argc, char *argv[])
{
int numOfBytes,fd,i;
if (argc != 2)
printf("Supply correct number of arguments.\n");
//exit(1);
fd =open("pattern.txt",O_RDWR);
if ( fd == -1 )
printf("File does not exist.\n");
//exit(1);
while ( (numOfBytes = read(fd,userBuf,MAXLENGTH)) > 0 )
;
printf("NumOfBytes = %d\n",numOfBytes);
for(i=0;userBuf[i] != '\0'; ++i)
{
if ( strstr(userBuf,argv[1]) )
printf("%s\n",userBuf);
}
}
The program is printing infinitely, the lines containing the pattern . I tried debugging , but couldn't figure out the error. Please let me know where am i wrong.,
Thanks
Say the string is "fooPATTERN". Your first time through the loop, you check for the pattern in "fooPATTERN" and find it. Then your second time through the loop, you check for the pattern in "ooPATTERN" and find it again. Then your third time, you check for the pattern in "oPATTERN" and find it again.
Since you're doing this to learn, I won't tell you much more. You can decide how best to solve it. There are at least two fundamentally different ways you could solve it. One is to do less on each pass of the loop to ensure you only find it once. The other is to make sure your next pass of the loop is past any pattern that was found.
One thing to think about: If the pattern is 'oo' and the string is 'ooo', how many patterns should be found? 1 or 2?
The 'read' does not delimit the data with a null character.
The while loop should encompase the for loop - it doesn't
First, you shouldn't be using raw Unix i/o with open and read if you're just learning C. Start with standard C i/o with fopen and fread/fscanf/fgets and so forth.
Second, you're reading in successive pieces of the file into the same buffer, overwriting the buffer each time, and only ever processing the last contents of the buffer.
Third, nothing guarantees that your buffer will be zero-terminated when you read into it with read(). In fact, it usually won't be.
Fourth, you're not using the i variable in the body of your loop. I can't tell exactly what you were shooting for here, but doing the same thing on the same data umpteen thousand times surely wasn't it.
Fifth, always compile with the fullest warning settings you can abide -- at lest -Wall with GCC. It should have complained that you call read() without including <unistd.h>.