Since OS X 10.8, NSImage has a block based initialiser to draw vector based content into a bitmap.
The idea is to provide a drawing handler that is called whenever a representation of the image is requested.
The relation between points and pixels is expressed by passing a NSSize (in points) to the initialiser and to explicitly set the pixel dimensions for the representation:
NSString* localDocuments = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES) objectAtIndex:0];
NSString* pdfPath = [localDocuments stringByAppendingPathComponent:@"1.pdf"];
NSData* pdfData = [NSData dataWithContentsOfFile:pdfPath];
NSPDFImageRep* pdfImageRep = [NSPDFImageRep imageRepWithData:pdfData];
CGFloat factor = 300/72;
NSInteger pageCount = [pdfImageRep pageCount];
for(int i = 0 ; i < pageCount ; i++)
{
[pdfImageRep setCurrentPage:i];
NSImage* scaledImage = [NSImage imageWithSize:pdfImageRep.size flipped:NO drawingHandler:^BOOL(NSRect dstRect) {
[pdfImageRep drawInRect:dstRect];
return YES;
}];
NSImageRep* scaledImageRep = [[scaledImage representations] firstObject];
/*
* The sizes of the PDF Image Rep and the [NSImage imageWithSize: drawingHandler:]-context
* are defined in terms of points.
* By explicitly setting the size of the scaled representation in Pixels, you
* define the relation between points & pixels.
*/
scaledImageRep.pixelsWide = pdfImageRep.size.width * factor;
scaledImageRep.pixelsHigh = pdfImageRep.size.height * factor;
NSBitmapImageRep* pngImageRep = [NSBitmapImageRep imageRepWithData:[scaledImage TIFFRepresentation]];
NSData* finalData = [pngImageRep representationUsingType:NSJPEGFileType properties:nil];
NSString* pageName = [NSString stringWithFormat:@"Page_%ld.jpg", (long)[pdfImageRep currentPage]];
[[NSFileManager defaultManager] createFileAtPath:[NSString stringWithFormat:@"%@%@", pdfPath, pageName] contents:finalData attributes:nil];
}