145 

   146 // this routine checks for the PNG size without loading it in memory

   147 // https://github.com/steipete/PSFramework/blob/master/PSFramework%20Version%200.3/PhotoshopFramework/PSMetaDataFunctions.m

   148 CGSize PSPNGSizeFromMetaData (NSString *aFileName) {

   149     // File Name to C String.

   150     const char *fileName = [aFileName UTF8String];

   151     // source file

   152     FILE *infile = fopen(fileName, "rb");

   153     if (infile == NULL) {

   154         DLog(@"Can't open the file: %@", aFileName);

   155         return CGSizeZero;

   156     }

   157 

   158     // Bytes Buffer.

   159     unsigned char buffer[30];

   160     // Grab Only First Bytes.

   161     fread(buffer, 1, 30, infile);

   162     // Close File.

   163     fclose(infile);

   164 

   165     // PNG Signature.

   166     unsigned char png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};

   167 

   168     // Compare File signature.

   169     if ((int)(memcmp(&buffer[0], &png_signature[0], 8))) {

   170         DLog(@"The file (%@) is not a PNG file", aFileName);

   171         return CGSizeZero;

   172     }

   173 

   174     // Calc Sizes. Isolate only four bytes of each size (width, height).

   175     int width[4];

   176     int height[4];

   177     for (int d = 16; d < (16 + 4); d++) {

   178         width[d-16] = buffer[d];

   179         height[d-16] = buffer[d+4];

   180     }

   181 

   182     // Convert bytes to Long (Integer)

   183     long resultWidth = (width[0] << (int)24) | (width[1] << (int)16) | (width[2] << (int)8) | width[3];

   184     long resultHeight = (height[0] << (int)24) | (height[1] << (int)16) | (height[2] << (int)8) | height[3];

   185 

   186     // Return Size.

   187     return CGSizeMake(resultWidth,resultHeight);

   188 }