nn::jpeg::CTR::JpegMpDecoder::GetMpRegionsToBuildJpegData Member Function

Syntax

#include <nn/jpeg.h>

bool GetMpRegionsToBuildJpegData(
     MpRegionsToBuildJpegData * pBuffer,
     const u8 * src,
     size_t srcSize
);

Arguments

Name Description
out pBuffer Specifies the buffer storing the region information.
in src Specifies the start of the individual image data.
in srcSize Specifies the size of src in bytes.

Return Values

When the function succeeds it returns true. Returns false on failure.
Use the GetLastError function to get the reason for failure.

Description

This function gets regional information used for rebuilding the JPEG data from the individual image data stored in MP format.

Simply put, individual image data in MP format has this structure: [(JPEG header) + (APP2) + (JPEG data)], where APP2 includes the MP format attribute information. Leave out APP2 and you get [(JPEG header) + (JPEG data)], which is JPEG data not in the MP format. This function gets pointers and byte sizes for the (JPEG header) and (JPEG data) memory regions.

Generally, [pointer to starting image + return value of GetMpImageOffset] is returned in the src argument, and the return value of GetMpImageSize is returned in the srcSize argument. Confirm beforehand that the region specified by src and srcSize is a valid region.

This function will fail if the MP type of the individual image is MP_TYPE_CODE_LARGE_THUMBNAIL_IMAGE_CLASS_1 or MP_TYPE_CODE_LARGE_THUMBNAIL_IMAGE_CLASS_2 because these types of images are for display on monitors and do not include MP format attribute information. The Exif information can be omitted from images for display on monitors, so such data are not used for the rebuilding of JPEG data.

This function only partially performs decoding and shared processing. Consequently, there are some functions you cannot call immediately after calling this function: the GetLastWidth, GetLastHeight, GetLastOutputBufferWidth, and GetLastOutputBufferHeight functions, and all functions that get EXIF information, such as the GetLastDateTime function. Calls to these functions will have undefined return values.

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