Steve hello thanks for the reply..
it happens that I did a dirty work around here.
at application launch I load the CGImageRef map depending on the device scale
factor, so if it is 2.0 i load a @2x map otherwise the SD map. then when
initializing the view which contains the and draw a portion of the map, I
divide the frame's with and height by the device scale factor, and then in the
draw method I translate the context by the
CGImageGetHeight(bc_itemImage)/scaleFactor , which at the end will will the
view's bound's height, but to be sure I always take the CGImageRef height which
never gets modified after doing transformation to the view.
Te results
a nice a sharp image is drawn in retina display, and its SD counterpart in the
normal device without scale factor.
I dunno if it was the best approach but it works.
Im trying to avoid using UIImage, because i needed to load a CGImageRef form
the map then convert to UIImage, so I wanted to skip one step here, + I dunno
what benefits I gain/lose by using CGImageRef instead of the UIImage facade.
Thanks for the reply once again
Gustavo
On Dec 15, 2010, at 9:10 PM, Steve Christensen wrote:
> I believe the issue is that CGImage just refers to an image with an effective
> scale factor of 1.0, no matter the device scale. It sounds like you need to
> somehow keep track of the image scale you're using so that you're always
> drawing at the correct size. One way would be to use +[UIImage imageNamed:],
> which will automatically load the correct version of your map image. When you
> draw that image, it does so with the scale in mind.
>
>
> On Dec 13, 2010, at 3:09 PM, Gustavo Pizano wrote:
>
>> Hello all.
>>
>> Im creating some views which draws a CGImage that is obtained from a Atlas
>> Map, (Big map containing all the images).
>>
>> for iPHone 4 I have this map 2 times bigger than the normal one, so if I
>> have a 2.0 scale on screen I load that one.
>>
>> What Im getting is that on iPhone 4 Im seeing all the views are drawing the
>> CGImage too big, like 2 times more. So i think this has something to do with
>> the 2.0 scale factor.
>>
>> what should I do in order to draw the CGImage properly sized?
>>
>> this is my drawing method which is working on iPad...
>>
>> CGContextRef context = UIGraphicsGetCurrentContext();
>>
>> CGContextSaveGState(context);
>> CGContextTranslateCTM(context, 0, CGImageGetHeight(bc_itemImage));
>> CGContextScaleCTM(context, 1.0, -1.0);
>> CGContextDrawImage(context, self.bounds, bc_itemImage);
>> CGContextRestoreGState(context);
>>
>> and this is my init method
>>
>> -(id)initWithImageFrame:(CGRect)imgFrame fromSheet:(CGImageRef)sheet{
>>
>> self = [super initWithFrame:CGRectMake(0, 0, imgFrame.size.width,
>> imgFrame.size.height)];
>> if(self){
>> bc_itemImage = CGImageCreateWithImageInRect(sheet,imgFrame);
>>
>> self.backgroundColor = [UIColor clearColor];
>> bc_isInBox = YES;
>> }
>>
>> return self;
>> }
>>
>> Thanks in advance for any help provided.
>>
>> Gustavo
>
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