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I am doing image processing in a scientific context. Whenever I need to save an image to the hard drive, I want to be able to reopen it at a later time and get exactly the data that I had before saving it. I exclusively use the PNG format, having always been under the impression that it is a lossless format. Is this always correct, provided I am not using the wrong bit-depth? Should encoder and decoder play no role at all? Specifically, the images I save
imwrite() function, e.g. cv2.imwrite("image.png", array)
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Both PNG and TIFF files benefit from lossless compression, meaning that no matter how often you save, open, or resize them, they'll maintain their quality. However, TIFF files offer users a choice between lossy and lossless compression, which can help reduce the file size if this is a priority.
The simple answer is that PNGs offer lossless compression and JPEG files don't. This means, unlike JPEGs, PNGs don't lose any of their image data when they're compressed. On the flipside, lossless compression tends to make PNGs much bigger files than JPEGs, so they require more storage space.
Unlike JPEG files that get terrible picture artifacts with heavy compression, PNG's use lossless compression, meaning compression doesn't impact image quality.
The PNG file format employs lossless compression, so re-saving the image multiple times (even with changes) will not cause a further degradation of image quality.
Is the PNG Format Lossless Since it Has a Compression Parameter? The PNG format is supposed to be a lossless format, but when you save an image as a PNG file, you are asked to choose a compression level. Does this mean that the PNG format is actually not lossless after all?
Most notably here is JPEG. Some keep all image information, these are called lossless. Lossless compression produces bigger files, but you have no changes to your graphic. Common lossless image formats are PNG, GIF or TIFF.
How to Make a PNG? Fotor’s online PNG maker offers an easy and fast way to generate PNG files. Upload your picture into Fotor to get started. Then click on the Background Remover tool and Fotor will automatically convert your image into a transparent PNG within seconds.
Since PNG's compression is fully lossless--and since it supports up to 48-bit truecolor or 16-bit grayscale--saving, restoring and re-saving an image will not degrade its quality, unlike standard JPEG (even at its highest quality settings). The encoder and decoder should not matter, in regards of reading the images correctly.
PNG is a lossless format by design:
Since PNG's compression is fully lossless--and since it supports up to 48-bit truecolor or 16-bit grayscale--saving, restoring and re-saving an image will not degrade its quality, unlike standard JPEG (even at its highest quality settings).
The encoder and decoder should not matter, in regards of reading the images correctly. (Assuming, of course, they're not buggy).
And unlike TIFF, the PNG specification leaves no room for implementors to pick and choose what features they'll support; the result is that a PNG image saved in one app is readable in any other PNG-supporting application.
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