I have an image with the worldfile like this:
0.298582141739
0.000000000000
0.000000000000
-0.298582141739
1283836.327077804830
6134835.890168172310
I think it is the projected coordinate system. I want to convert it to geographic coordinate system, because I want to know the latitude/longitude of each pixel of the image.
How to convert that? I check the worldfileread in the matlab, it can read both. But I did not find how to convert.
Could anyone know about that? Thank you.
I'd say you need to know the coordinate system of the map. The world file simply describes a generic affine transformation in the plane. This allows you to convert from image pixels to map coordinates or vice versa. From there to geographic coordinates depends on the map projection.
If you don't know that projection, you need to ask the creator of the image or make some wild guesses. If you know what the image depicts then you can rule out some map projections. For example if the image is of a city in the US, then the UTM cells for France probably won't apply. But chances are that there is a number of rather similar projections and coordinate systems in use for the depicted location, and deciding between these will be tough.
One thing you can already rule out: the world file does not directly map to geographic coordinates measured in degrees (in a equirectangular projection). That's because the upper left corner of the image would have an easting of 1283836.327077804830 and a northing of 6134835.890168172310 which doesn't make sense as degrees. It could be meters or something like that, but I doubt it: The first and fourth line have the same absolute value, so your pixels are square. So unless your picture displays something close to the equator or your picture looks highly distorted in terms of horizontal vs. vertical extents, I'd say this is not a geographic coordinate system.