A method for removing shade in an input image, the method comprising: obtaining a color input image by capturing a document; characterized in that the method further comprises estimating a shade component image in color, the shade component image in color representing shade components in the color input image, the shade components depending on an image capture environment in which the document has been captured; calculating a difference value between a pixel value of a target pixel in the color input image and a pixel value in the shade component image in color at a coordinate point identical to that of the target pixel, wherein the difference value is calculated for each of color channels; selecting a difference value that is greatest in difference among the difference values calculated respectively for the color channels, referring to a table by using the selected difference value, and acquiring a first correction rate that is used in common for the color channels of the target pixel from the table, wherein the first correction rate has a value between 0% and 100%, and the first correction rate decreases as the difference value that is acquired increases, such that a color of the target pixel in the color input image is not impaired by the removal of the shade component; and correcting the pixel value of the target pixel in the color input image based on the pixel value of the shade component image in color, the first correction rate and a second correction rate, wherein the pixel value of the target pixel is corrected for each of the color channels; wherein the second correction rate has a value between 0% and 100% and depends on a representative luminance value of the color input image, wherein the second correction rate decreases as the representative luminance value of the input image decreases, in order to prevent overcorrection, wherein the correcting includes multiplying a pixel value of each of the color channels constituting the target pixel by a ratio between a color value indicating a paper white color and a correction value calculated for each of the color channels, wherein the correction value is calculated by subtracting a specific expression from the color value indicating the paper white color, wherein the specific expression is calculated by multiplying a difference between the color value indicating the paper white color and the pixel value of each of the color channels constituting a pixel in the shade component image in color at the coordinate point identical to that of the target pixel with the first correction rate that is used in common for the color channels of the target pixel, and the second correction rate. obtaining a color input image by capturing a document; characterized in that the method further comprises estimating a shade component image in color, the shade component image in color representing shade components in the color input image, the shade components depending on an image capture environment in which the document has been captured; calculating a difference value between a pixel value of a target pixel in the color input image and a pixel value in the shade component image in color at a coordinate point identical to that of the target pixel, wherein the difference value is calculated for each of color channels; selecting a difference value that is greatest in difference among the difference values calculated respectively for the color channels, referring to a table by using the selected difference value, and acquiring a first correction rate that is used in common for the color channels of the target pixel from the table, wherein the first correction rate has a value between 0% and 100%, and the first correction rate decreases as the difference value that is acquired increases, such that a color of the target pixel in the color input image is not impaired by the removal of the shade component; and correcting the pixel value of the target pixel in the color input image based on the pixel value of the shade component image in color, the first correction rate and a second correction rate, wherein the pixel value of the target pixel is corrected for each of the color channels; wherein the second correction rate has a value between 0% and 100% and depends on a representative luminance value of the color input image, wherein the second correction rate decreases as the representative luminance value of the input image decreases, in order to prevent overcorrection, wherein the correcting includes multiplying a pixel value of each of the color channels constituting the target pixel by a ratio between a color value indicating a paper white color and a correction value calculated for each of the color channels, wherein the correction value is calculated by subtracting a specific expression from the color value indicating the paper white color, wherein the specific expression is calculated by multiplying a difference between the color value indicating the paper white color and the pixel value of each of the color channels constituting a pixel in the shade component image in color at the coordinate point identical to that of the target pixel with the first correction rate that is used in common for the color channels of the target pixel, and the second correction rate.