Resize NSImage doesn't reduce bytes ?

Question

I've tried several versions of this but resizing the image doesn't reduce the bytes ...

            var image = NSImage(data: data)!

            let new_width: CGFloat = 200
            let new_height = new_width * aspect
            
            
            let newSize = NSSize(width: new_width, height: new_height)

            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)
                image.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)
                
                image = resizedImage
            }

AppKit

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Posted by

Pendragon

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Answer 1

I think you have to use image compression API (for JPEG for instance) to effectively reduce the memory footprint.

Here, it is just changing the display.

Posted by

Claude31

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Answer 2

a. How do you examine the byte count of the original image? The copied image?

b. How do you ensure that the original image is deallocated?

Posted by

QuinceyMorris

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Answer 3

The Byte Count can come from the Data() or NSData() ".count". I created a custom NSImage Class to check when replacing the "image" with "resizedImage" that it does Deallocate / Deinitialize, will only work with "var" not "let" to make sure it's an optional value.

Posted by

Pendragon

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Answer 4

Yeh, was just creating a new sized image without resampled data, thanks.

Incase anyone wonders here's an update (also tried making data smaller by compression and jpeg not png) ...

        if let rep = NSBitmapImageRep(bitmapDataPlanes: nil,
                                      pixelsWide: Int(new_width),
                                      pixelsHigh: Int(new_height),
                                      bitsPerSample: 8,
                                      samplesPerPixel: 4,
                                      hasAlpha: true,
                                      isPlanar: false,
                                      colorSpaceName: NSColorSpaceName.deviceRGB,
                                      bytesPerRow: 0,
                                      bitsPerPixel: 0)
        {
            let ctx = NSGraphicsContext(bitmapImageRep: rep)
            NSGraphicsContext.saveGraphicsState()
            NSGraphicsContext.current = ctx
            let rect = NSRect(x: 0, y: 0, width: new_size.width, height: new_size.height)
            image.draw(in: rect)
            ctx?.flushGraphics()
            NSGraphicsContext.restoreGraphicsState()
            
            let compression_factor = 0.35
            let options: [NSBitmapImageRep.PropertyKey: Any] = [.compressionFactor: compression_factor]
            
            if let data = rep.representation(using: .jpeg, properties: options) {
                image = NSImage(data: data)!
            }

Posted by

Pendragon

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Resize NSImage doesn't reduce bytes ?

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