> JPEG is a standard; file size does not depend on what tool you use to create it. It's strictly dependent on the image itself, and the render settings you choose.
This is not correct. For both JPEG and PNG the compression ratio can depend on the tool.
For JPEG the reason is that the quantization tables are not fixed. The quantization tables dictates how information is thrown away, and as such is responsible for the lossy part of JPEG.
The JPEG standard merely contain recommended quantization tables, however a lot of research has gone into deriving better quantization tables, especially image-dependent (tailored) ones that can provide better compression for the same image quality, or better image quality for the same compressed size.
For PNG the standard defines five pixel filters used to transform pixel values into something more compressible. However it leaves the encoder free to decide which filter to use and when. Thus a simple encoder is free to use the "None" filter for everything, ie don't do any filtering.
In addition, the PNG standard allows for additional pixel filters to be registered as extensions. Thus encoders with more advanced pixel filters could potentially compress better than an encoder supporting only the standard filters.
This is not correct. For both JPEG and PNG the compression ratio can depend on the tool.
For JPEG the reason is that the quantization tables are not fixed. The quantization tables dictates how information is thrown away, and as such is responsible for the lossy part of JPEG.
The JPEG standard merely contain recommended quantization tables, however a lot of research has gone into deriving better quantization tables, especially image-dependent (tailored) ones that can provide better compression for the same image quality, or better image quality for the same compressed size.
For PNG the standard defines five pixel filters used to transform pixel values into something more compressible. However it leaves the encoder free to decide which filter to use and when. Thus a simple encoder is free to use the "None" filter for everything, ie don't do any filtering.
In addition, the PNG standard allows for additional pixel filters to be registered as extensions. Thus encoders with more advanced pixel filters could potentially compress better than an encoder supporting only the standard filters.