allow ppm files as inputs

- only run bmp.magicValid when path ends in bmp
 - remove uneeced header size constants

src/image.zig

@@ -5,9 +5,6 @@ const bmp = @import("bmp_valid.zig");
 
 const plugins = @import("plugin.zig");
 
-/// Approximate size of the BMP header, in bytes.
-pub const BMPHeaderSize: usize = 82000;
-
 /// Buffer size for main image copying.
 pub const BufferSize: usize = 300000;
 
@@ -284,6 +281,7 @@ pub const Image = struct {
         var magic = [2]u8{ 0, 0 };
         _ = try file.read(&magic);
 
+        if (std.mem.endsWith(u8, self.path, ".bmp"))
             try bmp.magicValid(&magic);
     }
 

src/runner.zig

@@ -89,7 +89,7 @@ pub const Runner = struct {
         // before loading the file into scritcher. for example, you can start
         // krita/gimp and make it export a bmp and while in the program you can
         // apply filters, etc.
-        if (!std.mem.endsWith(u8, load_path, ".bmp")) {
+        if (!std.mem.endsWith(u8, load_path, ".bmp") and !std.mem.endsWith(u8, load_path, ".ppm")) {
             std.debug.warn("Only BMP files are allowed to be loaded.\n");
             return RunError.NoBMP;
         }