I am showing PDF content on a view using this code using Quartz Sample:
// PDF page drawing expects a Lower-Left coordinate system, so we flip the coordinate system
// before we start drawing.
CGContextTranslateCTM(context, 0.0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// Grab the first PDF page
CGPDFPageRef page = CGPDFDocumentGetPage(pdf, pageNo);
// We're about to modify the context CTM to draw the PDF page where we want it, so save the graphics state in case we want to do more drawing
CGContextSaveGState(context);
// CGPDFPageGetDrawingTransform provides an easy way to get the transform for a PDF page. It will scale down to fit, including any
// base rotations necessary to display the PDF page correctly.
CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFCropBox, self.bounds, 0, true);
// And apply the transform.
CGContextConcatCTM(context, pdfTransform);
// Finally, we draw the page and restore the graphics state for further manipulations!
CGContextDrawPDFPage(context, page);
CGContextRestoreGState(context);
Using this all works fine. I want to set the margin for the PDF context, by default it showing 50 px margin in every side. I have tried CGContext methods but not got the appropriate one. Can anybody help me with this?
PDFs don't really have any concept of margins. If you're not the one responsible for the document's content then all you can really do is scale it down.
I got an answer for this here
CGContext pdf page aspect fit
Related
I was very surprised to not find the answer on Stackoverflow to this one.
I have a vector path in pdf format, like Safari or the Mac App Store apps usually use as image icons.
Now, I'd like to specify the fill-color and a custom shadow in code, rather than making images and exporting them. I didn't figure out how to do this.
The shadow works, however the fill color does not.
Can anyone tell me how to do this?
Current Code
[NSGraphicsContext saveGraphicsState];
{
// Has no effect
[[NSColor colorWithCalibratedRed:0.92f green:0.97f blue:0.98f alpha:1.00f] setFill];
// Neither has this
[[NSColor colorWithCalibratedRed:0.92f green:0.97f blue:0.98f alpha:1.00f] set];
NSShadow *shadow = [NSShadow new];
[shadow setShadowOffset:NSMakeSize(0, -1)];
[shadow setShadowColor:[NSColor blackColor]];
[shadow setShadowBlurRadius:3.0];
[shadow set];
[image drawInRect:imgRect
fromRect:NSZeroRect
operation:NSCompositeXOR
fraction:1.0
respectFlipped:YES
hints:nil];
}
[NSGraphicsContext restoreGraphicsState];
In terms of calling drawInRect:... the image "is what it is". Setting the fill and stroke will effect only primitive operations. A good way to think about this is to realize that all images, vector or raster, have to behave the same way; It would be weird for the current fill color that's set on the context to affect the drawing of a raster-based image, right? Same idea -- the image is the image. The vector image might also have multiple paths in it, each with different fills. It wouldn't make sense for those to be overridden by the fill color set on the context either.
The shadow works regardless because it's effectively a compositing operation; Drawing a given image with a given shadow setting produces the same shadow whether the image was raster-based or the vector equivalent thereof.
In short, if you want to change the contents of the image, you're going to have to write the code to extract the vectors from the image and then draw them as primitives.
Alternately, if all you want is to fill any filled areas with the color, you could use the vector image to create a mask on the context, then you could set the color
on the context, and fill. That might produce the desired effect.
I need to implement bubble chart in an iPad application with each bubble having user interaction (touch event) to navigate to a detailed view.
Is there any framework or a way to do so (like bargraph, piechart, linegraph using coreplot)??
I tried implementing manually even using CGContextRef for each bubble as below
CGContextRef c = UIGraphicsGetCurrentContext();
UIColor *grayColor = [UIColor colorWithRed:1 green:1 blue:1 alpha:0.5];
[grayColor set];
CGRect rectangle = CGRectMake(xaxis+2,yaxis+2,size-4,size-4);
CGContextSetLineWidth(c,4);
CGContextStrokeEllipseInRect(c, rectangle);
CGContextAddEllipseInRect(c, rectangle);
CGContextSetFillColorWithColor(c, [bubbleColor CGColor]);
CGContextFillPath(c);
but unable to crop the edges from having user interaction i.e, touch event (since these bubbles are circles inscribed in UIView's).
Thanks in Advance
You can use a scatter plot for this. Implement the -symbolForScatterPlot:recordIndex: datasource method to provide a custom plot symbol for each plot point. Vary the size, shape, fill, etc., of the symbols as desired based on the data.
Try this and this. Also, you could try OBShapedButton with your images. Hope this helps :)
I am having difficulties scaling the size of an image on an HTML canvas in GWT. I can successfully render an image using this:
ImageData id = context.createImageData(width, height);
-- do some image manipulation here...
context.putImageData(id, 0, 0);
That works great. But then I'd like to scale the size of the image, so I add this to the very next line:
context.scale(scale, scale);
But nothing happens to the image, it does not scale. What am I missing?
Here is an example on how to scale an image:
http://code.google.com/p/gwt-examples/wiki/gwt_hmtl5#Image_Scale_/_Resize
I need to convert each page of a PDF document to PNG images. These images are then displayed in a scrollView. I need to create two images per page: one at the screen dimension, and one 2.5 times bigger (it is used when the user zoom in the scrollView).
My problem is that I have sometimes memory warnings and crashes when I create big images.
The way I do it is well-known:
CGRect pageRect = CGPDFPageGetBoxRect(pdfPage, kCGPDFMediaBox);
float pdfScale = 2.5*self.view.frame.size.height/pageRect.size.height;
pageRect.size = CGSizeMake(pageRect.size.width*pdfScale, pageRect.size.height*pdfScale);
UIGraphicsBeginImageContext(pageRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBFillColor(context, 1.0,1.0,1.0,1.0);
CGContextFillRect(context,pageRect);
CGContextSaveGState(context);
CGContextTranslateCTM(context, 0.0, pageRect.size.height);
CGContextScaleCTM(context, pdfScale,-pdfScale);
CGContextDrawPDFPage(context, page);
CGContextRestoreGState(context);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
The problem occurs on iPhone 3G/3GS and iPod Touch.
How can I limit the memory consumption while still having a zoom scale of 2.5 ?
Thanks !
You could consider using a webview to display the PDF, that takes care of the zooming and memory issues. Basically rendering the vector format PDF to a bitmap PNG at a large size is possibly not the most appropriate design decision. Without knowing what your requirements for the PNG are though, it's hard to comment.
I have a PDF file that I want to draw in outline form. I want to draw the first several pages on the document each in their own UIImage to use on a button so that when clicked, the main display will navigate to the clicked page.
However, CGContextDrawPDFPage seems to be using copious amounts of memory when attempting to draw the page. Even though the image is only supposed to be around 100px tall, the application crashes while drawing one page in particular, which according to Instruments, allocates about 13 MB of memory just for the one page.
Here's the code for drawing:
//Note: This is always called in a background thread, but the autorelease pool is setup elsewhere
+ (void) drawPage:(CGPDFPageRef)m_page inRect:(CGRect)rect inContext:(CGContextRef) g {
CGPDFBox box = kCGPDFMediaBox;
CGAffineTransform t = CGPDFPageGetDrawingTransform(m_page, box, rect, 0,YES);
CGRect pageRect = CGPDFPageGetBoxRect(m_page, box);
//Start the drawing
CGContextSaveGState(g);
//Clip to our bounding box
CGContextClipToRect(g, pageRect);
//Now we have to flip the origin to top-left instead of bottom left
//First: flip y-axix
CGContextScaleCTM(g, 1, -1);
//Second: move origin
CGContextTranslateCTM(g, 0, -rect.size.height);
//Now apply the transform to draw the page within the rect
CGContextConcatCTM(g, t);
//Finally, draw the page
//The important bit. Commenting out the following line "fixes" the crashing issue.
CGContextDrawPDFPage(g, m_page);
CGContextRestoreGState(g);
}
Is there a better way to draw this image that doesn't take up huge amounts of memory?
Try to add :
CGContextSetInterpolationQuality(g, kCGInterpolationHigh);
CGContextSetRenderingIntent(g, kCGRenderingIntentDefault);
before :
CGContextDrawPDFPage(g, m_page);
I had a similar issue and adding the 2 function call above resulted in the rendering using 5x less memory. Might be a bug in the CGContextXXX drawing functions
Take a look at my code for a PDF image slicer on github:
http://github.com/luciuskwok/Maps-Slicer
There should be enough memory on the device that a 13 MB allocation isn't going to kill the app. Are you draining the autorelease pool each time you render a PDF? You might also want to cache the rendering into a UIImage so that it doesn't have to render it every time it's displayed.