Photoshop and other photo editing software provide various options when resizing pictures for the web. Jeff find the most appropriate setting for you:

When making an image smaller, use bicubic, which has a natural sharpening effect. You want to emphasize the data that remains in the new, smaller image after discarding all that extra detail from the original image.

When making an image larger, use bilinear, which has a natural smoothing effect. You want to blend over the interpolated fake detail in the new, larger image that never existed in the original image. Link

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