Image processing apparatus, image processing method, and image processing program

An image processing method comprising:

• calculating luminances for pixels that make up an image;
• calculating an average luminance of the luminances calculated at the luminance calculating;
• identifying, from among the luminances calculated at the luminance calculating, each of the luminances that has a value equal to or greater than a distinguishing value that functions to distinguish a bright portion from a dark portion in the image and calculating a ratio of the identified bright-portion luminances to the luminances of the image;
• calculating, in accordance with the luminance calculated at the luminance calculating, a distribution value indicating a dispersion level of a luminance distribution of pixels whose luminance value is equal to or greater than the distinguishing value;
• and
• performing a determination determining whether the average luminance calculated at the average luminance calculating is equal to or less than a first threshold, whether the bright-portion ratio calculated at the bright-portion ratio calculating is equal to or greater than a second threshold, and whether the distribution value calculated at the distribution value calculating is equal to or greater than a third threshold.

A image processing apparatus comprising:

• a memory;
• and
• a processor coupled to the memory, wherein the processor executes a process comprising:
• calculating luminances for pixels that make up an image;
• calculating an average luminance of the luminances calculated at the luminance calculating;
• identifying, from among the luminances calculated at the luminance calculating, each of the luminances that has a value equal to or greater than a distinguishing value that functions to distinguish a bright portion from a dark portion in the image and calculating a ratio of the identified bright-portion luminances to the luminances of the image;
• calculating, in accordance with the luminance calculated at the luminance calculating, a distribution value indicating a dispersion level of a luminance distribution of pixels whose luminance value is equal to or greater than the distinguishing value;
• and
• performs a determination determining whether the average luminance calculated at the average luminance calculating is equal to or less than a first threshold, whether the bright-portion ratio calculated at the bright-portion ratio calculating is equal to or greater than a second threshold, and whether the distribution value calculated at the distribution value calculating is equal to or greater than a third threshold.