Image processing apparatus

摘要

An image processing apparatus includes a histogram producing section for producing a histogram of density signal levels of pixels constituting the image data, a reference density signal level detecting section for detecting from the histogram a density signal level processed by the maximum number of the pixels in a range excluding the maximum value and the minimum value of the density signal levels, a density signal level conversion range determining section for successively comparing the number of the pixels of each density signal level with a threshold value from the density signal level processed by the maximum number of the pixels to lower density signal levels, thereby determining a density signal level lower limit value of density signal levels to be converted and successively comparing the number of the pixels of each density signal level with a threshold value from the maximum value of the density signal level to lower density signal levels, thereby determining a density signal level upper limit value of density signal levels to be converted, a density signal level conversion value calculating section for calculating a conversion value so that density signal levels between the density signal level lower limit value and the density signal level upper limit value can be converted to density signal levels ranging from white to black and a density signal level converting section for converting the density signal levels of the pixels in accordance with the conversion value. According to the thus constituted image processing apparatus, it is possible to reproduce an electron microscope image having a desired gradation.