I used cwebp to convert my jpg image to web. Now I am using dwebp to convert it back but its increasing in size from original one. Is there any way to control the file size in dwebp.
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Why not jus use your JPEG image on the web? – user3344003 Jan 17 '15 at 18:57
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I have huge size of JPEG image and some constraint with storage space. That's why i need webp images to work. – shilpi_agrawal Jan 18 '15 at 05:41
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Transcoding between lossy formats tends to increase the size unless the representation of data happens to be extremely compatible between the formats, be it audio, pictures, video or other lossy data. WebP uses a 4x4 Hadamard transform, whereas JPEG uses an 8x8 Discrete Cosine Transform (DCT). Quantization, which is the main form of data loss in these formats, produces different kind of artefacts in these transformations, and transcoding cannot be optimal. Particularly, if either WebP or JPEG was saved with extremely low quality, the other format will struggle to compete with it after transcoding -- the later format will not only have to codify the image signal, but the resulting artefacts from the other format, too.
So, while there is an inherent tendency for an increase in file size in such back-and-forth conversion, the exact amount of loss happening at every stage can be controlled. Which flags and tools (including versions) are you using exactly?
Jyrki Alakuijala
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