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Editorial Team
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Asked: 2026-05-20T10:47:22+00:00

The code below is intended to display the pages of a PDF while properly

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The code below is intended to display the pages of a PDF while properly handling any non-zero rotation angles that might be specified for each page. My test PDF file has multiple pages and one them has a 180 degree rotation angle, which the code properly detects, but the call to CGPDFPageGetDrawingTransform (followed by CGContextContactCTM) has no effect. The page is being displayed unrotated. What am I doing wrong?

CGContextSaveGState(context);

CGRect drawRect=self.bounds;
CGRect cropBox = CGPDFPageGetBoxRect(pdfPage, kCGPDFCropBox);

int rotationAngle=CGPDFPageGetRotationAngle(pdfPage);

if (kDebug>1) {
    NSLog(@"***** page rotation angle is %d",rotationAngle);
}

CGContextTranslateCTM(context, drawRect.origin.x, drawRect.origin.y);

CGAffineTransform transform = CGPDFPageGetDrawingTransform(pdfPage, kCGPDFCropBox, cropBox, rotationAngle, true);
CGContextConcatCTM (context, transform);

float xScaleFactor=drawRect.size.width / cropBox.size.width;
float yScaleFactor=drawRect.size.height / cropBox.size.height;

CGContextTranslateCTM(context, -CGRectGetMinX(cropBox), CGRectGetMaxY(cropBox)*yScaleFactor);
CGContextScaleCTM(context, xScaleFactor, -yScaleFactor);

CGContextClipToRect(context, cropBox);
CGContextDrawPDFPage(context, pdfPage);

CGContextRestoreGState(context);

Thanks,

//Scott

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1 Answer

  1. Editorial Team

    So after a careful re-reading of the API for CGPDFPageGetDrawingTransform, I discover that the value of page’s /ROTATE attribute is ADDED to the rotation angle you specify in the method call. In my situation above, the page’s /ROTATE happend to be 180. was grabbing that in the rotationAngle var and passing that in to get the transform. So, 180+180 = 360 = no visibile rotation.

    I now call GPDFPageGetDrawingTransform with a rotation angle of 0.0. Anything in the /ROTATE is added, and voila, I get the correct results.

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