I've noticed that line drawings from the drawing app I'm making are very low quality when saved using this code:
UIImage *imageToSave = drawImage.image;
UIImageWriteToSavedPhotosAlbum(imageToSave, nil, nil, nil);
As far as I can understand, you can't set the JPG quality when using UIImageWriteToSavedPhotosAlbum.
Is there a way to save the UIImage as a PNG to the photo library directly, or some way to increase the JPG quality? When doing a screenshot (pressing on/off+home on the iPad) the quality of the grabbed picture is perfect, but I can't expect people to save images that way.
Any help greatly appreciated!
Try this
NSData* pngdata = UIImagePNGRepresentation (drawImage.image); //PNG wrap
UIImage* img = [UIImage imageWithData:pngdata];
UIImageWriteToSavedPhotosAlbum(img, nil, nil, nil);
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I want save image to camera roll in apple Watch
this is my code:
UIImage *image = [UIImage imageNamed:#"w0-1.jpg"];
UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
can you help me please??
You cannot save image to saved photo album. You can only save image to your application folder.
I am writing an app process image. But when I change alpha of an image to 0, it mean that this image will be transparent. And then I save this image to photo library.
UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
But when I open this image again, i see that it has white background.
Does anybody know why?
Did you saved as jpeg?
try this:
NSData* pngdata = UIImagePNGRepresentation (image);
UIImage* img = [UIImage imageWithData:pngdata];
UIImageWriteToSavedPhotosAlbum(img, nil, nil, nil);
I am debugging a piece of code where an UIImage may be gone through UIImageJPEGRepresentation multiple times, I thought that must be a bug and the image quality will get worsen, but surprisingly we can't see the difference visually.
So I did a test, loading an image, and try to let it go through UIImageJPEGRepresentation 1000 times, surprisingly, whether 1 or 1000 times doesn't really make a difference in the image quality visually, why is that so?
This is the testing code:
UIImage *image = [UIImage imageNamed:#"photo.jpeg"];
// Create a data reference here for the for loop later
// First JPEG compression here
// I would imagine the data here already has low image quality
NSData *data = UIImageJPEGRepresentation(image, 0);
for(int i=0; i<1000; i++)
{
// Convert the data with low image quality to UIImage
UIImage *image = [UIImage imageWithData:data];
// Compress the image into a low quality data again
// at this point i would imagine the image get even more low quality, like u resaved a jpeg twice in phootshop
data = UIImageJPEGRepresentation(image, 0);
}
// up to this point I would imagine the "data" has gone through JPEG compression 1000 times
// like you resave a jpeg as a jpeg in photoshop 1000 times, it should look like a piece of crap
UIImage *imageFinal = [UIImage imageWithData:data];
UIImageView *view = [[UIImageView alloc] initWithImage:imageFinal];
[self.view addSubview:view];
// but it didn't, the final image looks like it has only gone through the jpeg compression once.
EDIT: my doubt can be summarised into a simpler code, if you do this in objectiveC:
UIImage *image1 = an image..
NSData *data1 = UIImageJPEGRepresentation(image1, 0);
UIImage *image2 = [UIImage imageWithData:data1];
NSData *data2 = UIImageJPEGRepresentation(image2, 0);
UIImage *imageFinal = [UIImage imageWithData:data2];
Did imageFinal gone through JPEG compression twice?
As you know, JPG compression works by altering the image to produce smaller file size. The reason why you don't see progressively worse quality is because you're using the same compression setting each time.
The algorithm alters the source image just enough to fit into the compression profile - in other words, compressing the result of 50% JPG again at 50% will produce the same image, because the image doesn't need to be altered any more.
You can test this in Photoshop - save a photo out at say 30% quality JPG. Reopen the file you just saved, and go to Save for Web - flip between PNG (uncompressed/original) and JPG 30% - there will be no difference.
Hope this helps.
All types of compression will ideally reduce the size of an image. There are two types of compression which describes how they affects images:
Lossy Compression:
Lossy compression will reduces the size of the image by removing some data from it. This generally cause, effect the quality of the image, which means it reduce your image quality
Lossless Compression:
Lossless compression reduce the size of the image by changing the way in which the data is stored. Therefore this type of compression will make no change in the image quality.
Please check out the compression type you are using.
This may help you in decrease the image size. put the number from yourself how many times you want to perform loop;
UIImage *image = [UIImage imageNamed:#"photo.jpeg"];
for(int i=100; i>0; i--)
{
UIImage *image = [UIImage imageWithData:data];
NSData *data = UIImageJPEGRepresentation(image, (0.1 * i);
NSLog(#"%d",data.length);
}
When I resave an image from camera roll, it is smaller than the original one :
same number of pixels, same width and height, same colorspace, same DPI,
but file size is less :
original = 2.5 MB
resaved one = 1.5 MB
I use this method :
UIImageWriteToSavedPhotosAlbum(imageTosave, self, nil, nil);
Is this normal ?
Thank you for your help .
I encountered this issue a while agoitand found a workaround. Try wrapping the image in a new png:
NSData* imageData = UIImagePNGRepresentation (yourOriginalImage); // get PNG representation
UIImage* image2 = [UIImage imageWithData:imagedata]; // wrap UIImage around PNG representation
UIImageWriteToSavedPhotosAlbum(image2, nil, nil, nil); // save to photo album
Please let me know if this workaround still works. If not, I will remove this answer.
I want to save an image to camera roll with my own imagename in ios 5.I am using AV Foundation for accessing camera features.Please help me with possible solutions.
// Image to save
UIImage *img = [UIImage imageNamed:#"ImageName.png"];
// Request to save the image to camera roll
UIImageWriteToSavedPhotosAlbum(img, self,
#selector(image:didFinishSavingWithError:contextInfo:), nil);
Hope this helps..