ImageMagick load image into RAM - imagemagick

Question

I have a JPG picture on which I'd like to perform some operations in order to use pattern recognition. The picture is being rotated and also some filters like color inversion, greyscale,.. are applied
The program goes like this
for(i=0;i<360;i++){
rotate(pic,i);
foreach(filter as f){
f(pic);
recognize(pic);
}
}
In order to increase speed I'd like to have the source image loaded in RAM and then read from there. Is it possible?

Answer 1

You can write the image to mpr:, or clone the image instance to a new structure. Regardless if where the original source is in memory, you will still need to copy the data in the first for loop. Here's an example, in C, that holds a wand instance and clones each iteration.
#include <stdio.h>
#include <MagickWand/MagickWand.h>
void rotate(MagickWand * wand, double degree) {
PixelWand * pwand = NewPixelWand();
PixelSetColor(pwand, "white");
MagickRotateImage(wand, pwand, degree);
DestroyPixelWand(pwand);
}
void _f(MagickWand * wand, FilterTypes filter) {
double x,y;
x = y = 0.0;
MagickResampleImage(wand, x, y, filter);
}
void recognize(MagickWand * wand) {
// ???
}
int main(int argc, const char * argv[]) {
MagickWandGenesis();
MagickWand * wand, * copy_wand;
wand = NewMagickWand();
MagickReadImage(wand, "rose:");
for ( int i = 0; i < 360 ; i++ ) {
copy_wand = CloneMagickWand(wand);
for ( FilterTypes f = UndefinedFilter; f < SentinelFilter; f++ ) {
_f(copy_wand, f);
recognize(copy_wand);
}
}
MagickWandTerminus();
return 0;
}
The MPR writes to a specific page in memory, and can be identified by a user defined label.
MagickReadImage(wand, "rose:");
MagickWriteImage(wand, "mpr:original"); // Save image to "original" label
for ( int i = 0; i < 360 ; i++ ) {
copy_wand = NewMagickWand();
MagickReadImage(copy_wand, "mpr:original"); // Read image from "original" label
for ( FilterTypes f = UndefinedFilter; f < SentinelFilter; f++ ) {
_f(copy_wand, f);
recognize(copy_wand);
}
copy_wand = DestroyMagickWand(copy_wand);
}
The last option I can think of is to copy the image pixel-data into memory, and re-reference it with each iteration. This allows some performance improvements, and I'm thinking OpenMP, but you'll loose a lot of helper methods.
MagickReadImage(wand, "rose:");
size_t w = MagickGetImageWidth(wand);
size_t h = MagickGetImageHeight(wand);
size_t data_length = w * h * 4;
char * data = malloc(data_length);
MagickExportImagePixels(wand, 0, 0, w, h, "RGBA", CharPixel, (void *)data);
for ( int i = 0; i < 360; i++ ) {
long * copy_data = malloc(data_length);
memcpy(copy_data, data, data_length);

Answer 2

As you haven't specified a language or an operating system, I'll show you how to do that with Magick++ in C++ in a Linux/OSX environment:
#include <Magick++.h>
#include <iostream>
using namespace std;
using namespace Magick;
int main(int argc,char **argv)
{
InitializeMagick(*argv);
// Create an image object
Image image;
// Read a file into image object
image.read( "input.gif" );
// Crop the image to specified size (width, height, xOffset, yOffset)
image.crop( Geometry(100,100, 0, 0) );
// Repage the image to forget it was part of something bigger
image.repage();
// Write the image to a file
image.write( "result.gif" );
return 0;
}
Compile with:
g++ -o program program.cpp `Magick++-config --cppflags --cxxflags --ldflags --libs`
You will need an image called input.gif for it to read and that should be bigger than 100x100, so create one with:
convert -size 256x256 xc:gray +noise random input.gif