Global tone mapping

A non-transitory computer-readable storage medium storing executable instructions that, when executed by a processor, cause performance of operations comprising operations to:

• access an image captured by an image sensor;
• compute a first histogram for luminance values of the image;
• access a target histogram for the image;
• compute a transfer function based on the first histogram and the target histogram such that when the transfer function is applied to pixel values of the image to create a set of modified luminance values, a histogram of the modified luminance values is within a threshold similarity of the target histogram;
• obtain scene classification information for the image;
• modify the transfer function based on the scene classification information, wherein modifying the transfer function comprises multiplying a difference of a gain of the transfer function and one by an adjustment parameter that is modulated as a function of the scene classification information;
• apply the transfer function to pixel values of the image to produce a tone mapped image;
• and
• output the tone mapped image.

A non-transitory computer-readable storage medium storing executable instructions that, when executed by a processor, cause performance of operations comprising operations to:

• access an image captured by an image sensor;
• compute a first histogram for luminance values of the image;
• access a target histogram for the image;
• compute a transfer function based on the first histogram and the target histogram such that when the transfer function is applied to pixel values of the image to create a set of modified luminance values, a histogram of the modified luminance values is within a threshold similarity of the target histogram;
• compute a derivative of the transfer function;
• adjust one of a high threshold area and a low threshold area of the derivative of the transfer function such that the high threshold area and the low threshold area are equal;
• modify the derivative of the transfer function by removing the high threshold area and the low threshold area from the derivative;
• compute a modified transfer function from the modified derivative of the transfer function;
• apply the modified transfer function to pixel values of the image to produce a tone mapped image;
• and
• output the tone mapped image.