Showing papers on "Tone mapping published in 2008"
01 Aug 2008
TL;DR: This paper advocates the use of an alternative edge-preserving smoothing operator, based on the weighted least squares optimization framework, which is particularly well suited for progressive coarsening of images and for multi-scale detail extraction.
Abstract: Many recent computational photography techniques decompose an image into a piecewise smooth base layer, containing large scale variations in intensity, and a residual detail layer capturing the smaller scale details in the image. In many of these applications, it is important to control the spatial scale of the extracted details, and it is often desirable to manipulate details at multiple scales, while avoiding visual artifacts.In this paper we introduce a new way to construct edge-preserving multi-scale image decompositions. We show that current basedetail decomposition techniques, based on the bilateral filter, are limited in their ability to extract detail at arbitrary scales. Instead, we advocate the use of an alternative edge-preserving smoothing operator, based on the weighted least squares optimization framework, which is particularly well suited for progressive coarsening of images and for multi-scale detail extraction. After describing this operator, we show how to use it to construct edge-preserving multi-scale decompositions, and compare it to the bilateral filter, as well as to other schemes. Finally, we demonstrate the effectiveness of our edge-preserving decompositions in the context of LDR and HDR tone mapping, detail enhancement, and other applications.
1,381 citations
01 Aug 2008
TL;DR: This work proposes a tone mapping operator that can minimize visible contrast distortions for a range of output devices, ranging from e-paper to HDR displays, and shows that the problem can be solved very efficiently by employing higher order image statistics and quadratic programming.
Abstract: We propose a tone mapping operator that can minimize visible contrast distortions for a range of output devices, ranging from e-paper to HDR displays. The operator weights contrast distortions according to their visibility predicted by the model of the human visual system. The distortions are minimized given a display model that enforces constraints on the solution. We show that the problem can be solved very efficiently by employing higher order image statistics and quadratic programming. Our tone mapping technique can adjust image or video content for optimum contrast visibility taking into account ambient illumination and display characteristics. We discuss the differences between our method and previous approaches to the tone mapping problem.
410 citations
TL;DR: The method consists of two modules: a camera-alignment module and a movement detector, which removes the ghosting effects in the HDRI created by moving objects.
Abstract: Automatic high-dynamic range image generation from low- dynamic range images offers a solution to conventional methods, which require a static scene. The method consists of two modules: a camera-alignment module and a movement detector, which removes the ghosting effects in the HDRI created by moving objects.
252 citations
01 Aug 2008
TL;DR: In this article, the human visual system is used to detect and classify visible changes in the image structure, and a new metric for image quality assessment is proposed based on the detection and classification of visible changes.
Abstract: The diversity of display technologies and introduction of high dynamic range imagery introduces the necessity of comparing images of radically different dynamic ranges. Current quality assessment metrics are not suitable for this task, as they assume that both reference and test images have the same dynamic range. Image fidelity measures employed by a majority of current metrics, based on the difference of pixel intensity or contrast values between test and reference images, result in meaningless predictions if this assumption does not hold. We present a novel image quality metric capable of operating on an image pair where both images have arbitrary dynamic ranges. Our metric utilizes a model of the human visual system, and its central idea is a new definition of visible distortion based on the detection and classification of visible changes in the image structure. Our metric is carefully calibrated and its performance is validated through perceptual experiments. We demonstrate possible applications of our metric to the evaluation of direct and inverse tone mapping operators as well as the analysis of the image appearance on displays with various characteristics.
234 citations
TL;DR: This work presents an overview about the effects of basic image attributes in high dynamic range tone mapping, and proposes a scheme of relationships between these attributes, leading to the definition of an overall image quality measure.
219 citations
Patent•
05 May 2008TL;DR: In this article, multiple images of a scene are captured at different exposure settings and a further image of an object placed in the scene is captured at one exposure setting, then a second radiance image is formed from the further image.
Abstract: Methods, image processors and imaging devices for capturing a high dynamic range (HDR) image. Multiple images of a scene are captured at respectively different exposure settings. A further image of an object placed in the scene is captured at one exposure setting. A first radiance image is formed from the multiple images. A second radiance image is formed from the further image. The first radiance image and the second radiance image are merged to form the HDR image.
124 citations
28 Jan 2008
TL;DR: In this article, a localized inverse tone mapping method is proposed for efficient inter-layer prediction, which applies a scaling factor and an offset to each macroblock, per color channel, and then the differences are entropy coded.
Abstract: This paper presents a technique for coding high dynamic range videos. The proposed coding scheme is scalable, such that both standard dynamic range and high dynamic range representations of a video can be extracted from one bit stream. A localized inverse tone mapping method is proposed for efficient inter-layer prediction, which applies a scaling factor and an offset to each macroblock, per color channel. The scaling factors and offsets are predicted from neighboring macroblocks, and then the differences are entropy coded. The proposed inter-layer prediction technique is independent of the forward tone mapping method and is able to cover a wide range of bit-depths and various color spaces. Simulations are performed based on H.264/AVC SVC common software and core experiment conditions. Results show the effectiveness of the proposed method.
78 citations
21 Apr 2008
TL;DR: An algorithm and related methods are introduced that expand the contrast range of Low Dynamic Range videos in order to regenerate missing High Dynamic Range (HDR) data by inverting established tone mapping operator.
Abstract: In this paper we introduce an algorithm and related methods that expand the contrast range of Low Dynamic Range (LDR) videos in order to regenerate missing High Dynamic Range (HDR) data. For content generated from single exposure LDR sequences, this is clearly an under constrained problem. We achieved the expansion by inverting established tone mapping operator, a process we term inverse tone mapping. This approach is augmented by a number of methods which help expand the luminance for the required pixels while avoiding artifacts. These methods may be used to convert the large libraries of available legacy LDR content for use, for instance, on new content-starved HDR devices. Moreover, these same methods may be used to provide animated emissive surfaces for image based lighting (IBL). We demonstrate results for all the above applications and validate the resultant HDR videos with original HDR references using the HDR Visual Difference Predictor (HDR-VDP) image metric.
67 citations
TL;DR: It is demonstrated that the majority of both global and local tone‐mapping operators can be well approximated by computationally inexpensive image processing operations, such as a per‐pixel tone curve, a modulation transfer function and color saturation adjustment.
Abstract: Although several new tone-mapping operators are proposed each year, there is no reliable method to validate their performance or to tell how different they are from one another. In order to analyze and understand the behavior of tone-mapping operators, we model their mechanisms by fitting a generic operator to an HDR image and its tone-mapped LDR rendering. We demonstrate that the majority of both global and local tone-mapping operators can be well approximated by computationally inexpensive image processing operations, such as a per-pixel tone curve, a modulation transfer function and color saturation adjustment. The results produced by such a generic tone-mapping algorithm are often visually indistinguishable from much more expensive algorithms, such as the bilateral filter. We show the usefulness of our generic tone-mapper in backward-compatible HDR image compression, the black-box analysis of existing tone mapping algorithms and the synthesis of new algorithms that are combination of existing operators.
59 citations
Patent•
09 Apr 2008
TL;DR: In this article, a joint inter-layer prediction among the available color channels is proposed for color bit depth scalability, where the interlayer prediction is a joint prediction based on all color components.
Abstract: For two or more versions of a video with different spatial, temporal or SNR resolution, scalability can be achieved by generating a base layer (BL) and an enhancement layer (EL). When a version of a video is available that has higher color bit depth than can be displayed, a common solution is tone mapping. A more efficient compression method is proposed for the case where the two or more versions with different color bit depth use different color encoding. The present invention is based on joint inter-layer prediction among the available color channels. Thus, color bit depth scalability can also be used where the two or more versions with different color bit depth use different color encoding. In this case the inter-layer prediction is a joint prediction based on all color components. Prediction may also include color space conversion and gamma correction.
58 citations
TL;DR: The experimental results show that the proposed high dynamic range imaging system has good performance on both tone and color reproduction.
Abstract: This paper presents an integrated color imaging system for taking images in extremely high dynamic range scenes. The system first fuses several differently exposed raw images to acquire more intensity information. The effective dynamic range of the image raw data can be extended to 256 times if five differently exposed images are fused. Then it runs edge detection iterations to extract the image details in different luminance levels. The proposed tone reproduction algorithm equalizes the histogram of the extracted fine edges which tends to assign larger dynamic range for highly populated regions. Finally, the local contrast enhancement is performed to further refine the image details. The experimental results show that the proposed high dynamic range imaging system has good performance on both tone and color reproduction.
01 Dec 2008
TL;DR: This work presents a simple and cost-efficient way of extending contrast, perceived tonal resolution, and color space of reflective media, such as paper prints, hardcopy photographs, or electronic paper displays, through a calibrated projector-camera system.
Abstract: We present a simple and cost-efficient way of extending contrast, perceived tonal resolution, and color space of reflective media, such as paper prints, hardcopy photographs, or electronic paper displays. A calibrated projector-camera system is applied for automatic registration, radiometric scanning and superimposition. A second modulation of the projected light on the surface of such media results in a high dynamic range visualization. This holds application potential for a variety of domains, such as radiology, astronomy, optical microscopy, conservation and restoration of historic art, modern art and entertainment installations.
06 Feb 2008
TL;DR: This work proposes an efficient global tone reproduction method that achieves robust results across a large variety of HDR images without the need to adjust parameters, which makes this method highly suitable for automated dynamic range compression, which for instance is necessary when a large number of HDR pictures need to be converted.
Abstract: In order to display images of high dynamic range (HDR), tone reproduction operators are usually applied that reduce the dynamic range to that of the display device. Generally, parameters need to be adjusted for each new image to achieve good results. Consistent tone reproduction across different images is therefore difficult to achieve, which is especially true for global operators and to some lesser extent also for local operators. We propose an efficient global tone reproduction method that achieves robust results across a large variety of HDR images without the need to adjust parameters. Consistency and efficiency make our method highly suitable for automated dynamic range compression, which for instance is necessary when a large number of HDR images need to be converted.
TL;DR: It is demonstrated that the characterization method is very accurate even in unknown illumination conditions, effectively turning a digital camera into a measurement device that measures physically accurate radiance values — both in terms of luminance and color — rivaling more expensive measurement instruments.
Abstract: In this paper we present a new practical camera characterization technique to improve color accuracy in high dynamic range (HDR) imaging. Camera characterization refers to the process of mapping device-dependent signals, such as digital camera RAW images, into a well-defined color space. This is a well-understood process for low dynamic range (LDR) imaging and is part of most digital cameras — usually mapping from the raw camera signal to the sRGB or Adobe RGB color space. This paper presents an efficient and accurate characterization method for high dynamic range imaging that extends previous methods originally designed for LDR imaging. We demonstrate that our characterization method is very accurate even in unknown illumination conditions, effectively turning a digital camera into a measurement device that measures physically accurate radiance values — both in terms of luminance and color — rivaling more expensive measurement instruments.
Patent•
04 Aug 2008TL;DR: In this article, the authors present a method capable of real-time implementable local tone mapping of high dynamic range images using a modified Reinhard operator, where such a method utilizes, in part, a modified Reinhard operator.
Abstract: The present invention relates to a method capable of real-time implementable local tone mapping of high dynamic range images. In one embodiment, the present invention relates to a method capable of accomplishing real-time local tone mapping of high dynamic range images so that they have clear details without, for example, halo artifacts when viewed on standard display devices. In another embodiment, the present invention relates to a method capable of accomplishing real-time local tone mapping of high dynamic range images so that they have clear details without, for example, halo artifacts when viewed on standard display devices where such a method utilizes, in part, a modified Reinhard operator.
20 Jun 2008
TL;DR: A novel and efficient tone mapping algorithm for converting high dynamic range images back to low dynamic range (LDR) images for displaying purpose because of the limited contrast ratio of common displays and printers is presented.
Abstract: This paper presents a novel and efficient tone mapping algorithm for converting high dynamic range (HDR) images back to low dynamic range (LDR) images for displaying purpose because of the limited contrast ratio of common displays and printers. As the ratio between the maximum and minimum values of common HDR images is always very large and also the population usually deflects to one side, for convenient processing, most researchers first take the logarithm on the luminance layer or use another adaptive mapping to shorter the range of the distribution in their tone mapping methods. However, these mappings have already distorted the original imagespsila characteristics. In this paper, there is no such adverse mapping applied on the luminance layer in the proposed tone mapping algorithm. The paper does produce a tone reproduction curve to convert HDR images to LDR images. Adaptive techniques are also manipulated to provide better visual quality. The whole process is automatic and no parameter is required for manual input. The result will be a superior visual quality tone mapped LDR image with original HDR imagepsilas characteristics.
Patent•
05 May 2008
TL;DR: In this paper, a high tone image is saved in a versatile image file format to enhance usability, where an imaging unit that images an original image having a predetermined dynamic range, which is a ratio between minimum luminance and maximum luminance, is provided an image generating part that generates a synthesized image data that is higher in tone than a tone width of the original image by synthesizing a plurality of original images imaged under different imaging conditions at the same observation position.
Abstract: A high tone image is saved in a versatile image file format to enhance usability. There are provided an imaging unit that images an original image having a predetermined dynamic range, which is a ratio between minimum luminance and maximum luminance; a synthesized image generating part that generates a synthesized image data that is higher in tone than a tone width of the original image by synthesizing a plurality of original images imaged under different imaging conditions at the same observation position; a display unit that displays the images imaged by the imaging unit; a tone conversion part that converts the synthesized image data generated by the synthesized image generating part to low tone image data having a tone width capable of being displayed on the display unit; and a tone data saving part that generates a high tone data-attached display file including a high tone image region for saving the synthesized image data serving as a basis as an image file for saving the low tone image data.
TL;DR: This work proposes a complete digital camera workflow to capture and render high dynamic range (HDR) static scenes, from RAW sensor data to an output-referred encoded image based on a model of retinal processing.
Abstract: We propose a complete digital camera workflow to capture and render high dynamic range (HDR) static scenes, from RAW sensor data to an output- referred encoded image. In traditional digital camera processing, demosaicing is one of the first operations done after scene analysis. It is followed by rendering operations, such as color correction and tone mapping. Our approach is based on a model of retinal processing of the human visual system (HVS). In the HVS, rendering operations, including adaptation, are performed directly on the cone responses, which corresponds to a mosaic image. Our workflow conforms more closely to the retinal processing model, performing all rendering before demosaicing.. This reduces the complexity of the computation, as only one third of the pixels are processed. This is especially important as our tone mapping operator applies local and global tone corrections, which is usually needed to well render high dynamic scenes. Our algorithms efficiently process HDR images with different keys and different content.
27 Jan 2008
TL;DR: This work presents a promising combination of both technologies, a high dynamic range multispectral camera featuring a higher color accuracy, an improved signal to noise ratio and greater dynamic range compared to a similar low dynamic range camera.
Abstract: Capturing natural scenes with high dynamic range content using conventional RGB cameras generally results in saturated and underexposed and therefore compromising image areas. Furthermore the image lacks color accuracy due to a systematic color error of the RGB color filters. The problem of the limited dynamic range of the camera has been addressed by high dynamic range imaging1, 2 (HDRI): Several RGB images of different exposures are combined into one image with greater dynamic range. Color accuracy on the other hand can be greatly improved using multispectral cameras,3 which more accurately sample the electromagnetic spectrum. We present a promising combination of both technologies, a high dynamic range multispectral camera featuring a higher color accuracy, an improved signal to noise ratio and greater dynamic range compared to a similar low dynamic range camera.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: This work discusses how to construct and control improved tone-mapping functions that enhance visibility of image details in the dark regions while not excessively compressing the image in the bright image parts.
Abstract: For real-time imaging with digital video cameras and high-quality with TV display systems, good tonal rendition of video is important to ensure high visual comfort for the user. Except local contrast improvements, High Dynamic Range (HDR) scenes require adaptive gradation correction (tone-mapping function), which should enable good visualization of details at lower brightness. We discuss how to construct and control improved tone-mapping functions that enhance visibility of image details in the dark regions while not excessively compressing the image in the bright image parts. The result of this method is a 21-dB expansion of the dynamic range thanks to improved SNR by using multiple- exposure techniques. This new algorithm was successfully evaluated in HW and outperforms the existing algorithms with 11 dB. The new scheme can be successfully applied to cameras and TV systems to improve their contrast.
Patent•
06 May 2008
TL;DR: In this article, an image brightness control device is proposed to improve the definition of brightness so as to correspond to the characteristic of the input image, by automatically considering how to reflect a distribution characteristic of an image.
Abstract: Provided are an image brightness control device and an image brightness control method for improving the definition of brightness of the entire image and/or improving the definition of brightness of local areas using local brightness information. The image brightness controlling device includes: a preprocessing unit acquiring an offset table for controlling a dynamic range corresponding to an image range of an input image using brightness values of color data of the input image; and a tone mapping unit mapping the offset table onto the color data. It is possible to improve the definition of brightness so as to correspond to the characteristic of the input image, by automatically considering how to reflect a distribution characteristic of an image.
12 May 2008
TL;DR: This paper presents an encoding scheme for HDR images, which significantly reduces their storage requirements, with a negligible loss of information, and model an HDR image as a piecewise linear function of its tone-mapped version.
Abstract: With advent of high dynamic range (HDR) imaging techniques, it has been possible to capture natural scenes in larger details. HDR images are tone-mapped to lower dynamic range (LDR) versions for displaying on paper or a screen. Details lost during tone-mapping are important for certain existing and future applications, and need to be preserved. However, the size of HDR images is very large and that gives rise to need of effective encoding techniques. In this paper, we present an encoding scheme for HDR images, which significantly reduces their storage requirements, with a negligible loss of information. We model an HDR image as a piecewise linear function of its tone-mapped version. The tone-mapped image and the error in modeling are stored as LDR images, and these two along with the created model, approximate the HDR image. Comparison with the existing state of the art technique is given to show the effectiveness of our proposed scheme.
Patent•
10 Jul 2008TL;DR: In this article, a method of compressing a stream of video frame data wherein tone mapping functions are determined for video frames of said stream, said tone mapping function being different from one another for frames relating to different scenes and wherein it is suggested that the tone mapping functionality will be altered for frames of the stream relating to the same scene.
Abstract: The invention relates to a method of compressing a stream of video frame data wherein tone mapping functions are determined for video frames of said stream, said tone mapping functions being different from one another for frames relating to different scenes and wherein it is suggested that the tone mapping functions will be altered for frames of the stream relating to the same scene.
27 Jan 2008
TL;DR: The novel method of adaptive sharpening aimed for photo printers is proposed, which includes 3 key techniques: sharpness level estimation, local tone mapping and boosting of local contrast.
Abstract: Sharpness is an important attribute that contributes to the overall impression of printed photo quality. Often it is
impossible to estimate sharpness prior to printing. Sometimes it is a complex task for a consumer to obtain accurate
sharpening results by editing a photo on a computer.
The novel method of adaptive sharpening aimed for photo printers is proposed. Our approach includes 3 key techniques:
sharpness level estimation, local tone mapping and boosting of local contrast. Non-reference automatic sharpness level
estimation is based on analysis of variations of edges histograms, where edges are produced by high-pass filters with
various kernel sizes, array of integrals of logarithm of edges histograms characterizes photo sharpness, machine learning
is applied to choose optimal parameters for given printing size and resolution. Local tone mapping with ordering is
applied to decrease edge transition slope length without noticeable artifacts and with some noise suppression. Unsharp
mask via bilateral filter is applied for boosting of local contrast. This stage does not produce strong halo artifact which is
typical for the traditional unsharp mask filter.
The quality of proposed approach is evaluated by surveying observer's opinions. According to obtained replies the
proposed method enhances the majority of photos.
01 Dec 2008
TL;DR: A new tone mapping algorithm for the display of high dynamic range images, inspired by adaptive process of the human visual system, based on the center-surround Retinex processing, which preserves visibility and contrast impression of highynamic range scenes in the common display devices.
Abstract: In this paper, we present a new tone mapping algorithm for the display of high dynamic range images, inspired by adaptive process of the human visual system. The proposed algorithm is based on the center-surround Retinex processing. In our method, the local details are enhanced according to a non-linear adaptive spatial filter (Gaussian filter), whose shape (filter variance) is adapted to high-contrast edges of the image. Thus our method does not generate halo artifacts meanwhile preserves visibility and contrast impression of high dynamic range scenes in the common display devices. The proposed method is tested on a variety of HDR images and the results show the good performance of our method in terms of visual quality.
Patent•
12 May 2008TL;DR: In this article, a tone mapping technique is used to combine the luminance information of pixels in corresponding locations of the images according to a tone map technique to generate a high dynamic range image.
Abstract: Generating a high dynamic range image includes obtaining a maximum luminance and a minimum luminance of a scene to be captured, setting a first range of exposure values and a second range of exposure values according to the maximum luminance and the minimum luminance, capturing a first image of the scene according to the first range of exposure values and a second image of the scene according to the second range of exposure values, and superposing the images by compositing luminance information of pixels in corresponding locations of the images according to a tone mapping technique.
TL;DR: A novel tone mapping operator (TMO) for high dynamic range (HDR) images is presented, starting from an algorithm for low dynamic range image enhancement and color correction called ACE (automatic color enhancement), and introducing new features to correctly handle the high variation of HDR images.
Abstract: In this article we present a novel tone mapping operator (TMO) for high dynamic range (HDR) images. Starting from an algorithm for low dynamic range image enhancement and color correction called ACE (automatic color enhancement), we keep its differential and local behavior, introducing new features to correctly handle the high variation of HDR images. In particular, we add a nonlinear local regulator able to automatically tune the algorithm parameters on image variations. In this way, the algorithm behavior changes according to local variations. Moreover, a key setting feature has been added to control the output appearance; it automatically proposes an appropriate key value for the final spatial invariant display mapping. The proposed method performs the spatial variant filtering using only one parameter, that tunes output detail visibility versus overall contrast. We propose a default setting, that guarantees a good solution in most cases. Test, results, and comparison are presented. © 2008 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 17, 285–294, 2007
Patent•
22 Sep 2008
TL;DR: In this paper, local shading of fine contrast variations in an image, with particular advantage in tone mapping applications, is performed by the preferred degree of increased image contrast 810, including compensation for subsequent tone mapping, and the difference between a profile signal 803 and the image signal 801 conditional on the signal profile level being higher than the original image signal level, wherein avoiding boosting of brightness level to obtain contrast enhancement.
Abstract: Methods and apparatuses of contrast enhancement on an image are disclosed. The method performs local shading of fine contrast variations in an image, with particular advantage in tone mapping applications. The amounts of shading are determined by the preferred degree of increased image contrast 810, including compensation for subsequent tone mapping, and the difference between a profile signal 803 and the image signal 801 conditional on the signal profile level being higher than the original image signal level, wherein avoiding boosting of brightness level to obtain contrast enhancement. The profile signal 803 is calculated by the weighted sum of the image signal and the absolute signal variation which is the absolute value of the variation between the brightness of two neighbor pixels. This amount of shading is reduced to zero when the profile signal 803 is lower than the original image signal 801 for avoiding the overshooting problem at sharp edges in an image. Uniform RGB scaling is applied to preserve original color tones.
TL;DR: Different dynamic range reduction techniques known from the tone mapping of optical images are examined, regarding their applicability to SAR data, and incorporated into the interactive visualization framework based on programmable graphics hardware.
Abstract: The visualization of synthetic aperture radar (SAR) data involves the mapping from high dynamic range amplitude values to gray values of a lower dynamic range display device. This dynamic range reduction process controls the amount of information in the displayed result and is therefore an important part of each SAR visualization system. Interactive systems provide the user with immediate feedback on the changes of the reduction method and its parameters. In this letter, we examine different dynamic range reduction techniques known from the tone mapping of optical images. The techniques are analyzed, regarding their applicability to SAR data, and incorporated into our interactive visualization framework based on programmable graphics hardware.
Patent•
05 May 2008
TL;DR: In this paper, a high tone image is saved in a versatile image file format to enhance usability, where an imaging unit that images an original image having a predetermined dynamic range, which is a ratio between minimum luminance and maximum luminance, is provided an image generating part that generates a synthesized image data that is higher in tone than a tone width of the original image by synthesizing a plurality of original images imaged under different imaging conditions at the same observation position.
Abstract: A high tone image is saved in a versatile image file format to enhance usability. There are provided an imaging unit that images an original image having a predetermined dynamic range, which is a ratio between minimum luminance and maximum luminance; a synthesized image generating part that generates a synthesized image data that is higher in tone than a tone width of the original image by synthesizing a plurality of original images imaged under different imaging conditions at the same observation position; a display unit that displays the images imaged by the imaging unit; a tone conversion part that converts the synthesized image data generated by the synthesized image generating part to low tone image data having a tone width capable of being displayed on the display unit; and a tone data saving part that generates a high tone data-attached display file including a high tone image region for saving the synthesized image data serving as a basis as an image file for saving the low tone image data.