How to give folder of images as input to Magick++ api? - c++

Question

I am need of passing a folder of images as input to Magick++ api. It can be done using mogrify in commandline as shown in post "ImageMagick script to resize folder of images". Reading a single image could be done through api call as
Image image(inputimage)
But how could we do the same for a folder of images? Can anyone help me with the respective api call?

Answer 1

That feature is not included in the Magick++ API. You will need to iterate the directory yourself and then use the Magick++ API to read and write the image. You can find an example on how to iterate through a folder in C/C++ in the following Stack Overflow post: How can I get the list of files in a directory using C or C++?.

Answer 2

I believe you would be responsible of reading the directory. The C library dirent.h is the first thing I think of, but I'm sure there's better C++/system/framework techniques.
#include <iostream>
#include <vector>
#include <dirent.h>
#include <Magick++.h>
int main(int argc, const char * argv[]) {
std::vector<Magick::Image> stack; // Hold images found
DIR * dir_handler = opendir("/tmp/images"); // Open dir
struct dirent * dir_entry;
if (dir_handler != NULL)
{
// Iterate over entries in directory
while ( (dir_entry = readdir(dir_handler)) != NULL ) {
// Only act on regular files
if (dir_entry->d_type == DT_REG) {
// Concatenate path (could be better)
std::string filename("/tmp/images/");
filename += dir_entry->d_name;
// Read image at path
stack.push_back(Magick::Image(filename));
}
}
closedir(dir_handler); // House keeping
} else {
// Handle DIR error
}
// Append all images into single montage
Magick::Image output;
Magick::appendImages(&output, stack.begin(), stack.end());
output.write("/tmp/all.png");
return 0;
}
There's also ExpandFilenames(int *,char ***) in the MagickCore library.
// Patterns to scan
int pattern_count = 1;
// First pattern
char pattern[PATH_MAX] = "/tmp/images/*.png";
// Allocate memory for list of patterns
char ** dir_pattern = (char **)MagickCore::AcquireMagickMemory(sizeof(char *));
// Assign first pattern
dir_pattern[0] = pattern;
// Expand patterns
Magick::MagickBooleanType ok;
ok = MagickCore::ExpandFilenames(&pattern_count, &dir_pattern);
if (ok == Magick::MagickTrue) {
std::vector<Magick::Image> stack;
// `pattern_count' now holds results count
for ( int i = 0; i < pattern_count; ++i) {
// `dir_pattern' has been re-allocated with found results
std::string filename(dir_pattern[i]);
stack.push_back(Magick::Image(filename));
}
Magick::Image output;
Magick::appendImages(&output, stack.begin(), stack.end());
output.write("/tmp/all.png");
} else {
// Error handle
}