我有一个NSBitmapImageRepxW大小H的。
我创建NSImage并调用addRepresentation:. 然后我需要调整NSImage.
我尝试setSize了方法，但它不起作用。我应该怎么办？
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26227 次
10 回答
41
编辑： 由于这个答案仍然是公认的答案，但没有考虑到 Retina 屏幕，我将直接链接到一个更好的解决方案：Objective-C Swift 4
因为 Paresh 的方法是完全正确的，但自 10.8 以来已弃用，我将在下面发布有效的 10.8 代码。不过，所有功劳都归功于 Paresh 的回答。
- (NSImage *)imageResize:(NSImage*)anImage newSize:(NSSize)newSize {
NSImage *sourceImage = anImage;
[sourceImage setScalesWhenResized:YES];
// Report an error if the source isn't a valid image
if (![sourceImage isValid]){
NSLog(@"Invalid Image");
} else {
NSImage *smallImage = [[NSImage alloc] initWithSize: newSize];
[smallImage lockFocus];
[sourceImage setSize: newSize];
[[NSGraphicsContext currentContext] setImageInterpolation:NSImageInterpolationHigh];
[sourceImage drawAtPoint:NSZeroPoint fromRect:CGRectMake(0, 0, newSize.width, newSize.height) operation:NSCompositingOperationCopy fraction:1.0];
[smallImage unlockFocus];
return smallImage;
}
return nil;
}
于 2013-07-01T01:54:43.240 回答
36
Thomas Johannesmeyer 的回答 using lockFocusdoesn't work as you may want on Retina/HiDPI screen: it resizing to the desired points in the native scale, not pixels。
- 如果要调整大小以在屏幕上显示，请使用该方法。
- 如果您正在为具有精确像素尺寸的文件调整大小，则在 Retina (2x DPI) 屏幕上运行时，文件大小将是原来的两倍。
此方法由各种答案（包括此相关问题中的一些答案）拼凑而成，无论当前屏幕 DPI 如何，都将大小调整为指定的像素尺寸：
+ (NSImage *)resizedImage:(NSImage *)sourceImage toPixelDimensions:(NSSize)newSize
{
if (! sourceImage.isValid) return nil;
NSBitmapImageRep *rep = [[NSBitmapImageRep alloc]
initWithBitmapDataPlanes:NULL
pixelsWide:newSize.width
pixelsHigh:newSize.height
bitsPerSample:8
samplesPerPixel:4
hasAlpha:YES
isPlanar:NO
colorSpaceName:NSCalibratedRGBColorSpace
bytesPerRow:0
bitsPerPixel:0];
rep.size = newSize;
[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithBitmapImageRep:rep]];
[sourceImage drawInRect:NSMakeRect(0, 0, newSize.width, newSize.height) fromRect:NSZeroRect operation:NSCompositeCopy fraction:1.0];
[NSGraphicsContext restoreGraphicsState];
NSImage *newImage = [[NSImage alloc] initWithSize:newSize];
[newImage addRepresentation:rep];
return newImage;
}
于 2016-07-18T17:31:17.540 回答
33
@Marco用Swift 4编写的答案：
extension NSImage {
func resized(to newSize: NSSize) -> NSImage? {
if let bitmapRep = NSBitmapImageRep(
bitmapDataPlanes: nil, pixelsWide: Int(newSize.width), pixelsHigh: Int(newSize.height),
bitsPerSample: 8, samplesPerPixel: 4, hasAlpha: true, isPlanar: false,
colorSpaceName: .calibratedRGB, bytesPerRow: 0, bitsPerPixel: 0
) {
bitmapRep.size = newSize
NSGraphicsContext.saveGraphicsState()
NSGraphicsContext.current = NSGraphicsContext(bitmapImageRep: bitmapRep)
draw(in: NSRect(x: 0, y: 0, width: newSize.width, height: newSize.height), from: .zero, operation: .copy, fraction: 1.0)
NSGraphicsContext.restoreGraphicsState()
let resizedImage = NSImage(size: newSize)
resizedImage.addRepresentation(bitmapRep)
return resizedImage
}
return nil
}
}
let targetSize = NSSize(width: 256.0, height: 256.0)
let newImageResized = myimage.resized(to: targetSize)
于 2017-03-20T22:42:31.910 回答
17
编辑您可以使用以下功能调整图像大小：
- (NSImage *)imageResize:(NSImage*)anImage
newSize:(NSSize)newSize
{
NSImage *sourceImage = anImage;
[sourceImage setScalesWhenResized:YES];
// Report an error if the source isn't a valid image
if (![sourceImage isValid])
{
NSLog(@"Invalid Image");
} else
{
NSImage *smallImage = [[[NSImage alloc] initWithSize: newSize] autorelease];
[smallImage lockFocus];
[sourceImage setSize: newSize];
[[NSGraphicsContext currentContext] setImageInterpolation:NSImageInterpolationHigh];
[sourceImage compositeToPoint:NSZeroPoint operation:NSCompositeCopy];
[smallImage unlockFocus];
return smallImage;
}
return nil;
}
其次像这样：
NSData *imageData = [yourImg TIFFRepresentation]; // converting img into data
NSBitmapImageRep *imageRep = [NSBitmapImageRep imageRepWithData:imageData]; // converting into BitmapImageRep
NSDictionary *imageProps = [NSDictionary dictionaryWithObject:[NSNumber numberWithFloat:0.9] forKey:NSImageCompressionFactor]; // any number betwwen 0 to 1
imageData = [imageRep representationUsingType:NSJPEGFileType properties:imageProps]; // use NSPNGFileType if needed
NSImage *resizedImage = [[NSImage alloc] initWithData:imageData]; // image created from data
于 2012-08-14T09:37:31.120 回答
15
实际上没有必要修改任何源图像参数，如size. 以下片段已经在 Swift 中，但我认为您可以从中推断出 Objective-C 版本：
func resized(to: CGSize) -> NSImage {
let img = NSImage(size: to)
img.lockFocus()
defer {
img.unlockFocus()
}
if let ctx = NSGraphicsContext.current {
ctx.imageInterpolation = .high
draw(in: NSRect(origin: .zero, size: to),
from: NSRect(origin: .zero, size: size),
operation: .copy,
fraction: 1)
}
return img
}
于 2015-05-24T10:11:25.823 回答
4
这是Thomas Johannesmeyer 回答的 Swift 4 版本：
func resize(image: NSImage, w: Int, h: Int) -> NSImage {
var destSize = NSMakeSize(CGFloat(w), CGFloat(h))
var newImage = NSImage(size: destSize)
newImage.lockFocus()
image.draw(in: NSMakeRect(0, 0, destSize.width, destSize.height), from: NSMakeRect(0, 0, image.size.width, image.size.height), operation: NSCompositingOperation.sourceOver, fraction: CGFloat(1))
newImage.unlockFocus()
newImage.size = destSize
return NSImage(data: newImage.tiffRepresentation!)!
}
和 Swift 4 版本的Marco 的回答：
func resize(image: NSImage, w: Int, h: Int) -> NSImage {
let destSize = NSMakeSize(CGFloat(w), CGFloat(h))
let rep = NSBitmapImageRep(bitmapDataPlanes: nil, pixelsWide: Int(destSize.width), pixelsHigh: Int(destSize.height), bitsPerSample: 8, samplesPerPixel: 4, hasAlpha: true, isPlanar: false, colorSpaceName: .calibratedRGB, bytesPerRow: 0, bitsPerPixel: 0)
rep?.size = destSize
NSGraphicsContext.saveGraphicsState()
if let aRep = rep {
NSGraphicsContext.current = NSGraphicsContext(bitmapImageRep: aRep)
}
image.draw(in: NSMakeRect(0, 0, destSize.width, destSize.height), from: NSZeroRect, operation: NSCompositingOperation.copy, fraction: 1.0)
NSGraphicsContext.restoreGraphicsState()
let newImage = NSImage(size: destSize)
if let aRep = rep {
newImage.addRepresentation(aRep)
}
return newImage
}
于 2018-02-03T20:09:19.060 回答
3
2020 | 斯威夫特 4 和 5：
用法：
let resizedImg = someImage.resizedCopy(w: 500.0, h:500.0)
let scaledImg = someImage.scaledCopy( sizeOfLargerSide: 1000.0)
//and bonus:
scaledImg.writePNG(toURL: someUrl )
代码：
extension NSImage {
func scaledCopy( sizeOfLargerSide: CGFloat) -> NSImage {
var newW: CGFloat
var newH: CGFloat
var scaleFactor: CGFloat
if ( self.size.width > self.size.height) {
scaleFactor = self.size.width / sizeOfLargerSide
newW = sizeOfLargerSide
newH = self.size.height / scaleFactor
}
else{
scaleFactor = self.size.height / sizeOfLargerSide
newH = sizeOfLargerSide
newW = self.size.width / scaleFactor
}
return resizedCopy(w: newW, h: newH)
}
func resizedCopy( w: CGFloat, h: CGFloat) -> NSImage {
let destSize = NSMakeSize(w, h)
let newImage = NSImage(size: destSize)
newImage.lockFocus()
self.draw(in: NSRect(origin: .zero, size: destSize),
from: NSRect(origin: .zero, size: self.size),
operation: .copy,
fraction: CGFloat(1)
)
newImage.unlockFocus()
guard let data = newImage.tiffRepresentation,
let result = NSImage(data: data)
else { return NSImage() }
return result
}
public func writePNG(toURL url: URL) {
guard let data = tiffRepresentation,
let rep = NSBitmapImageRep(data: data),
let imgData = rep.representation(using: .png, properties: [.compressionFactor : NSNumber(floatLiteral: 1.0)]) else {
Swift.print("\(self) Error Function '\(#function)' Line: \(#line) No tiff rep found for image writing to \(url)")
return
}
do {
try imgData.write(to: url)
}catch let error {
Swift.print("\(self) Error Function '\(#function)' Line: \(#line) \(error.localizedDescription)")
}
}
}
于 2020-07-16T02:09:58.330 回答
3
完整的 Swift 3 答案（从上面的@Erik Aigner 修改）：
extension NSImage {
func resizeImage(width: CGFloat, _ height: CGFloat) -> NSImage {
let img = NSImage(size: CGSize(width:width, height:height))
img.lockFocus()
let ctx = NSGraphicsContext.current()
ctx?.imageInterpolation = .high
self.draw(in: NSMakeRect(0, 0, width, height), from: NSMakeRect(0, 0, size.width, size.height), operation: .copy, fraction: 1)
img.unlockFocus()
return img
}
}
于 2017-02-07T22:14:38.887 回答
2
这是一个 Swift 3 版本的图像保持比例，只需将 minimumSize 设置为您想要的最小高度或宽度：
func imageResized(image: NSImage) -> NSImage {
let ratio = image.size.height / image.size.width
let width: CGFloat
let height: CGFloat
// We keep ratio of image
if ratio > 1 {
width = minimumSize
height = minimumSize * ratio
} else {
width = minimumSize
height = minimumSize * (1 / ratio)
}
let destSize = NSSize(width: width, height: height)
let newImage = NSImage(size: destSize)
newImage.lockFocus()
image.draw(in: NSRect(x: 0, y: 0, width: destSize.width, height: destSize.height), from: NSRect(x: 0, y: 0, width: image.size.width, height: image.size.height), operation: .sourceOver, fraction: 1.0)
newImage.unlockFocus()
newImage.size = destSize
return NSImage(data: newImage.tiffRepresentation!)!
}
于 2017-08-10T20:09:00.220 回答
1
仅用于缩放 NSBitmapImageRep
static NSBitmapImageRep *i_scale_bitmap(const NSBitmapImageRep *bitmap, const uint32_t width, const uint32_t height)
{
NSBitmapImageRep *new_bitmap = NULL;
CGImageRef dest_image = NULL;
CGColorSpaceRef space = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
CGContextRef context = CGBitmapContextCreate(NULL, (size_t)width, (size_t)height, PARAM(bitsPerComponent, 8), PARAM(bytesPerRow, (size_t)(width * 4)), space, kCGImageAlphaPremultipliedLast);
CGImageRef src_image = [bitmap CGImage];
CGRect rect = CGRectMake((CGFloat)0.f, (CGFloat)0.f, (CGFloat)width, (CGFloat)height);
CGContextDrawImage(context, rect, src_image);
dest_image = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(space);
new_bitmap = [[NSBitmapImageRep alloc] initWithCGImage:dest_image];
CGImageRelease(dest_image);
return new_bitmap;
}
以及基于 NSBitmapImageRep 缩放 NSImage
ImageImp *imgimp_create_scaled(const ImageImp *image, const uint32_t new_width, const uint32_t new_height)
{
NSImage *src_image = (NSImage*)image;
NSBitmapImageRep *src_bitmap, *dest_bitmap;
NSImage *scaled_image = nil;
cassert_no_null(src_image);
cassert([[src_image representations] count] == 1);
cassert([[[src_image representations] objectAtIndex:0] isKindOfClass:[NSBitmapImageRep class]]);
src_bitmap = (NSBitmapImageRep*)[[(NSImage*)image representations] objectAtIndex:0];
cassert_no_null(src_bitmap);
dest_bitmap = i_scale_bitmap(src_bitmap, new_width, new_height);
scaled_image = [[NSImage alloc] initWithSize:NSMakeSize((CGFloat)new_width, (CGFloat)new_height)];
[scaled_image addRepresentation:dest_bitmap];
cassert([scaled_image retainCount] == 1);
[dest_bitmap release];
return (ImageImp*)scaled_image;
}
直接在 NSImage 上绘制（[NSImage lockFocus] 等）将创建一个 NSCGImageSnapshotRep 而不是 NSBitmapImageRep。
于 2018-08-02T10:07:55.637 回答