Is there a way to a take a screenshot (low level quality) on osx programmatically?
I developed a function like below:
CGImageRef resizeImage(CGImageRef imageRef) {
CGRect thumRect;
CGPoint point;
point.x = 0;
point.y = 0;
thumRect.origin = point;
thumRect.size.height = 225;
thumRect.size.width = 360;
CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef);
if (aplhaInfo == kCGImageAlphaNone)
alphaInfo = kCGImageAlphaNoneSkipLast;
CGContextRef bitmap = CGBitmapContextCreate(NULL, thumRect.size.width, thumRect.size.height, CGImageGetBitsPerComponent(imageRef), 4 * thumRect.size.width, CGImageGetColorSpace(imageRef), alphaInfo);
CGContextDrawImage(bitmap, thumRect, imageRef);
imageRef = CGBitmapContextCreateImage(bitmap);
CGContextRelease(bitmap);
return imageRef;
}
When I runned this function, I took an between 150KB and 600KB image. If I decrease thumRect size, I cant read any characters in the image. But, I want to decrease these images as low as possible. Is there any suggestion or another possible solution?
Thanks.
I found a solution like below:
First af all, resize your image with code in my question.
Then Compress it :)
//imageRef is CGImageRef
NSImage * image = [[NSImage alloc] initWithCGImage:imageRef size:NSZeroSize];
NSBitmapImageRep *bmpImageRep = [NSBitmapImageRep imageRepWithData [image TIFFRepresentation]];
CGFloat compressionFactor = 1.0 //Read it : (1)
NSDictionary *jpgProperties = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithDouble:compressionFactor], NSImageCompressionFactor, [NSNumber numberWithBool:NO], NSImageProgressive, nil];
NSData *jpgData = [bmpImageRep representationUsingType:NSJPEGFileType properties:jpgProperties];
(1):https://developer.apple.com/library/mac/documentation/Cocoa/Reference/ApplicationKit/Classes/NSBitmapImageRep_Class/index.html#//apple_ref/doc/constant_group/Bitmap_image_properties
Related
I'm building an OS X app that needs to save the file to disk.
I'm currently using NSBitmapImageRep to represent the image in my code, and while saving the image to disk with representationUsingType:properties: method, I want to set the hasAlpha channel for the image, but the properties dictionary does not seem to support this.
So, I've tried to create a no-alpha bitmap representation, but according to many SO questions, the 3 channel/24 bits combination is not supported. Well, what should I do then?
Big thanks!
First off, I would try just making sure you create your NSBitmapImageRep with
-initWithBitmapDataPlanes:... hasAlpha:NO ...
And write it out and see if it the result doesn’t have alpha—one would kind of hope so.
If you’re trying to write out an image that has alpha, but not write the alpha, just copy it into a non-alpha image first, and write that out.
`
NSURL *url = [NSURL fileURLWithPath:name];
CGImageSourceRef source;
NSImage *srcImage =[[NSImage alloc] initWithContentsOfURL:url];;
NSLog(#"URL: %#",url);
source = CGImageSourceCreateWithData((__bridge CFDataRef)[srcImage TIFFRepresentation], NULL);
CGImageRef imageRef = CGImageSourceCreateImageAtIndex(source, 0, NULL);
CGRect rect = CGRectMake(0.f, 0.f, CGImageGetWidth(imageRef), CGImageGetHeight(imageRef));
CGContextRef bitmapContext = CGBitmapContextCreate(NULL,
rect.size.width,
rect.size.height,
CGImageGetBitsPerComponent(imageRef),
CGImageGetBytesPerRow(imageRef),
CGImageGetColorSpace(imageRef),
kCGImageAlphaNoneSkipLast | kCGBitmapByteOrder32Little
);
CGContextDrawImage(bitmapContext, rect, imageRef);
CGImageRef decompressedImageRef = CGBitmapContextCreateImage(bitmapContext);
NSImage *finalImage = [[NSImage alloc] initWithCGImage:decompressedImageRef size:NSZeroSize];
NSData *imageData = [finalImage TIFFRepresentation];
NSBitmapImageRep *imageRep = [NSBitmapImageRep imageRepWithData:imageData];
NSDictionary *imageProps = [NSDictionary dictionaryWithObject:[NSNumber numberWithFloat:0.9] forKey:NSImageCompressionFactor];
imageData = [imageRep representationUsingType:NSPNGFileType properties:imageProps];
[imageData writeToFile:name atomically:NO];
CGImageRelease(decompressedImageRef);
CGContextRelease(bitmapContext);
`
ref:
https://github.com/bpolat/Alpha-Channel-Remover
I've been able to adapt some code found on SO to produce an animated GIF from the "screenshots" of my view, but the results are unpredictable. GIF frames are sometimes full images, full frames ("replace" mode, as GIMP marks it), other times are just a "diff" from previous layer ("combine" mode).
From what I've seen, when there are fewer and/or smaller frames involved, the CG writes the GIF in "combine" mode, but failing to get the colors right. Actually, the moving parts are colored correctly, the background is wrong.
When CG saves the GIF as full frames, the colors are ok. The file size is larger, but hey, obviously you cannot have the best of both worlds. :)
Is there a way to either:
a) force CG to create "full frames" when saving the GIF
b) fix the colors (color table?)
What I do is (ARC mode):
capture the visible part of the view with
[[scrollView contentView] dataWithPDFInsideRect:[[scrollView contentView] visibleRect]];
convert and resize it to NSImageBitmapRep of PNG type
-(NSMutableDictionary*) pngImageProps:(int)quality {
NSMutableDictionary *pngImageProps;
pngImageProps = [[NSMutableDictionary alloc] init];
[pngImageProps setValue:[NSNumber numberWithBool:NO] forKey:NSImageInterlaced];
double compressionF = 1;
[pngImageProps setValue:[NSNumber numberWithFloat:compressionF] forKey:NSImageCompressionFactor];
return pngImageProps;
}
-(NSData*) resizeImageToData:(NSData*)data toDimX:(int)xdim andDimY:(int)ydim withQuality:(int)quality{
NSImage *image = [[NSImage alloc] initWithData:data];
NSRect inRect = NSZeroRect;
inRect.size = [image size];
NSRect outRect = NSMakeRect(0, 0, xdim, ydim);
NSImage *outImage = [[NSImage alloc] initWithSize:outRect.size];
[outImage lockFocus];
[image drawInRect:outRect fromRect:inRect operation:NSCompositeCopy fraction:1];
NSBitmapImageRep* bitmapRep = [[NSBitmapImageRep alloc] initWithFocusedViewRect:outRect];
[outImage unlockFocus];
NSMutableDictionary *imageProps = [self pngImageProps:quality];
NSData* imageData = [bitmapRep representationUsingType:NSPNGFileType properties:imageProps];
return [imageData copy];
}
get the array of BitmapReps and create the GIF
-(CGImageRef) pngRepDataToCgImageRef:(NSData*)data {
CFDataRef imgData = (__bridge CFDataRef)data;
CGDataProviderRef imgDataProvider = CGDataProviderCreateWithCFData (imgData);
CGImageRef image = CGImageCreateWithPNGDataProvider(imgDataProvider, NULL, true, kCGRenderingIntentDefault);
return image;
}
////////// create GIF from
NSArray *images; // holds all BitmapReps
CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)[NSURL fileURLWithPath:pot],
kUTTypeGIF,
allImages,
NULL);
// set frame delay
NSDictionary *frameProperties = [NSDictionary
dictionaryWithObject:[NSDictionary
dictionaryWithObject:[NSNumber numberWithFloat:0.2f]
forKey:(NSString *) kCGImagePropertyGIFDelayTime]
forKey:(NSString *) kCGImagePropertyGIFDictionary];
// set gif color properties
NSMutableDictionary *gifPropsDict = [[NSMutableDictionary alloc] init];
[gifPropsDict setObject:(NSString *)kCGImagePropertyColorModelRGB forKey:(NSString *)kCGImagePropertyColorModel];
[gifPropsDict setObject:[NSNumber numberWithBool:YES] forKey:(NSString *)kCGImagePropertyGIFHasGlobalColorMap];
// set gif loop
NSDictionary *gifProperties = [NSDictionary
dictionaryWithObject:gifPropsDict
forKey:(NSString *) kCGImagePropertyGIFDictionary];
// loop through frames and add them to GIF
for (int i=0; i < [images count]; i++) {
NSData *imageData = [images objectAtIndex:i];
CGImageRef imageRef = [self pngRepDataToCgImageRef:imageData];
CGImageDestinationAddImage(destination, imageRef, (__bridge CFDictionaryRef) (frameProperties));
}
// save the GIF
CGImageDestinationSetProperties(destination, (__bridge CFDictionaryRef)(gifProperties));
CGImageDestinationFinalize(destination);
CFRelease(destination);
I've checked the ImageBitmapReps, when saved as PNG individually, they are just fine.
As I understood, the color tables should be handled by CG or am I responsible to produce the dithered colors? How to do that?
Even when doing the same animation repeatedly, the GIFs produced may vary.
This is a single BitmapRep
(source: andraz.eu)
And this is the GIF with the invalid colors ("combine" mode)
(source: andraz.eu)
I read your code. Please double check the "allImages" while you are creating the CGImageDestinationRef, and the "[images count]".
the follow test code works fine:
NSDictionary *prep = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:[NSNumber numberWithFloat:0.2f] forKey:(NSString *) kCGImagePropertyGIFDelayTime] forKey:(NSString *) kCGImagePropertyGIFDictionary];
CGImageDestinationRef dst = CGImageDestinationCreateWithURL((__bridge CFURLRef)(fileURL), kUTTypeGIF, [filesArray count], nil);
for (int i=0;i<[filesArray count];i++)
{
//load anImage from array
...
CGImageRef imageRef=[anImage CGImageForProposedRect:nil context:nil hints:nil];
CGImageDestinationAddImage(dst, imageRef,(__bridge CFDictionaryRef)(prep));
}
bool fileSave = CGImageDestinationFinalize(dst);
CFRelease(dst);
I have a bit of an issue with applying a sharpening filter on a UIImage.
The code works perfectly but the problem that the resulting UIImage has an Alpha channel. This in turn causes some performance issues.
This is how I initialise my context and filter
EAGLContext *myEAGLContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
NSMutableDictionary *options = [[NSMutableDictionary alloc] init];
[options setObject: [NSNull null] forKey: kCIContextWorkingColorSpace];
context = [CIContext contextWithEAGLContext:myEAGLContext options:options];
sharpenLuminanceFilter = [CIFilter filterWithName:#"CISharpenLuminance"];
And I use the following function to generate an image
- (UIImage *)applySharpingFilter:(UIImage *)originalImage withValue:(float)value{
CIImage *image = [CIImage imageWithCGImage:originalImage.CGImage];
[sharpenLuminanceFilter setValue:image forKey:#"inputImage"];
[sharpenLuminanceFilter setValue:[NSNumber numberWithFloat:value] forKey:#"inputSharpness"];
CIImage * result = sharpenLuminanceFilter.outputImage;
CGImageRef cgimg = [context createCGImage:result fromRect:[result extent]];
double scaleFactor = [UIScreen mainScreen].scale;
UIImage *finalImage = [UIImage imageWithCGImage:cgimg scale:scaleFactor orientation:UIImageOrientationUp];
CGImageRelease(cgimg);
[sharpenLuminanceFilter setValue:nil forKey:#"inputImage"];
return finalImage;
}
Is there anyway I can specify that I want the resulting Image to be OPAQUE and have no alpha channel?
You can use a CIColorMatrix filter. Set the matrix to identity and the bias to [0, 0, 0, 1], and it should add 1 to the alpha, which will cause it to be solid.
I'd be curious to know in which way an alpha channel is affecting your performance.
I have a Cocoa Mac image editing app which lets users export JPEG images. I'm currently using the following code to export these images as JPEG files:
//this is user specified
NSInteger resolution;
NSImage* savedImage = [[NSImage alloc] initWithSize:NSMakeSize(600, 600)];
[savedImage lockFocus];
//draw here
[savedImage unlockFocus];
NSBitmapImageRep* savedImageBitmapRep = [NSBitmapImageRep imageRepWithData:[savedImage TIFFRepresentationUsingCompression:NSTIFFCompressionNone factor:1.0]];
NSDictionary* properties = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithFloat:1.0], NSImageCompressionFactor, nil];
//holds the jpeg file
NSData * imageData = nil;
imageData = [savedImageBitmapRep representationUsingType:NSJPEGFileType properties:properties];
However, I would like for the user to be able to provide the pixels per inch for this JPEG image (like you can in Photoshop's export options). What would I need to modify in the above code to adjust this value for the exported JPEG?
I couldn't find a way to do it with the NSImage APIs but CGImage can by setting kCGImagePropertyDPIHeight/Width.
I also set kCGImageDestinationLossyCompressionQuality which I think is the same as NSImageCompressionFactor.
//this is user specified
NSInteger resolution = 100;
NSImage* savedImage = [[NSImage alloc] initWithSize:NSMakeSize(600, 600)];
[savedImage lockFocus];
//draw here
[savedImage unlockFocus];
NSBitmapImageRep* savedImageBitmapRep = [NSBitmapImageRep imageRepWithData:[savedImage TIFFRepresentationUsingCompression:NSTIFFCompressionNone factor:1.0]];
NSDictionary* properties = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithFloat:1.0], kCGImageDestinationLossyCompressionQuality,
[NSNumber numberWithInteger:resolution], kCGImagePropertyDPIHeight,
[NSNumber numberWithInteger:resolution], kCGImagePropertyDPIWidth,
nil];
NSMutableData* imageData = [NSMutableData data];
CGImageDestinationRef imageDest = CGImageDestinationCreateWithData((CFMutableDataRef) imageData, kUTTypeJPEG, 1, NULL);
CGImageDestinationAddImage(imageDest, [savedImageBitmapRep CGImage], (CFDictionaryRef) properties);
CGImageDestinationFinalize(imageDest);
// Do something with imageData
if (![imageData writeToFile:[#"~/Desktop/test.jpg" stringByExpandingTildeInPath] atomically:NO])
NSLog(#"Failed to write imageData");
For NSImage or NSImageRep you do not set the resolution directly but set the size instead.
For size, numberOfPixels and resolution the following equation holds:
size = numberOfPixels * 72.0 / resolution
size is a length and is expressed in dots with the unit inch/72.
(size and resolution are floats). You can see that for an image with dpi=72 size and numberOfPixels are numerally the same (but the meaning is very different).
After creating an NSBitmapImageRep the size with the desired resolution can be set:
NSBitmapImageRep* savedImageBitmapRep = . . . ; // create the new rep
NSSize newSize;
newSize.width = [savedImageBitmapRep pixelsWide] * 72.0 / resolution; // x-resolution
newSize.height = [savedImageBitmapRep pixelsHigh] * 72.0 / resolution; // y-resolution
[savedImageBitmapRep setSize:newSize];
// save the rep
Two remarks: do you really need the lockFocus / unlockFocus way? The preferred way to build a new NSBitmapImageRep is to use NSGraphicsContext. see : http://www.mail-archive.com/cocoa-dev#lists.apple.com/msg74857.html
And: to use TIFFRepresentation for an NSBitmapImageRep is very time and space consuming. Since 10.6 another
way exists and costs nothing, because lockFocus and unlockFocus create an object of class NSCGImageSnapshotRep which under the hood is a CGImage. (In OS versions before 10.6 it was an NSCachedImageRep.) The following does it:
[anImage lockFocus];
// draw something
[anImage unlockFocus];
// now anImage contains an NSCGImageSnapshotRep
CGImageRef cg = [anImage CGImageForProposedRect:NULL context:nil hints:nil];
NSBitmapImageRep *newRep = [[NSBitmapImageRep alloc] initWithCGImage:cg];
// set the resolution
// here you may NSLog anImage, cg and newRep
// save the newRep
// release the newRep if needed
I am getting this exception while retriving data from address book. I have check through internet but not get any help for that.
Overflow allocating bitmap backing store. Cannot back bitmap with 320 bytes per row, -2147483648 height, and 1 planes
I am using AddressBook Framework for retriving data from Address Book. is this issue of Memory or it due to getting information of avatar that i have set in Addressbook contact.
Please help. If any suggestion or recommendations for it then please give it...
Thanks for your reply
As you have said, I have checked all the code for drawing large an image or view. And found the below function that i have used for resizing image. Now resizing image will be done on server side. I have more doubts for this issue. You can check it in below block of code. Now waiting from customer for this issue.
Thanks again for your help.
-(NSData *)getCompressedImageDataFromData:(NSData *)imData
{
NSImage *pImage = [[[NSImage alloc] initWithData:imData] autorelease];
NSSize orgSize = [pImage size];
int widthInput, heightInput;
widthInput = orgSize.width;
heightInput = orgSize.height;
if(widthInput <= 72 && heightInput <= 72)
return imData;
double newheight = heightInput;
NSSize newSize;
if(widthInput >= 72)
{
double ratio;
ratio = widthInput / heightInput;
newheight = 72 / ratio;
newSize = NSMakeSize (72, newheight);
}
else
newSize = NSMakeSize(widthInput, newheight);
NSImage *outputImage = [[[NSImage alloc] initWithSize:newSize] autorelease];
if(![outputImage isValid])
return nil;
[outputImage lockFocus];
[[NSGraphicsContext currentContext] setImageInterpolation:NSImageInterpolationHigh];
[pImage drawInRect:NSMakeRect(0, 0, newSize.width, newSize.height)
fromRect:NSZeroRect operation:NSCompositeCopy fraction:1.0];
[outputImage unlockFocus];
NSData *imageData = [outputImage TIFFRepresentationUsingCompression:NSTIFFCompressionJPEG factor:0];
return [imageData mutableCopy];
}
Are you creating one large view or image into which you're drawing multiple contacts in the address book? It sounds like you're trying to create too large an image/view.