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I got it to work using the following code for memory to memory compression. <pre><code>#include <stdio.h> #include "jpeg/jpeglib.h" /* This a custom destination manager for jpeglib that enables the use of memory to memory compression. See IJG documentation for details. */ typedef struct { struct jpeg_destination_mgr pub; /* base class */ JOCTET* buffer; /* buffer start address */ int bufsize; /* size of buffer */ size_t datasize; /* final size of compressed data */ int* outsize; /* user pointer to datasize */ int errcount; /* counts up write errors due to buffer overruns */ } memory_destination_mgr; typedef memory_destination_mgr* mem_dest_ptr; /* ------------------------------------------------------------- */ /* MEMORY DESTINATION INTERFACE METHODS */ /* ------------------------------------------------------------- */ /* This function is called by the library before any data gets written */ METHODDEF(void) init_destination (j_compress_ptr cinfo) { mem_dest_ptr dest = (mem_dest_ptr)cinfo->dest; dest->pub.next_output_byte = dest->buffer; /* set destination buffer */ dest->pub.free_in_buffer = dest->bufsize; /* input buffer size */ dest->datasize = 0; /* reset output size */ dest->errcount = 0; /* reset error count */ } /* This function is called by the library if the buffer fills up I just reset destination pointer and buffer size here. Note that this behavior, while preventing seg faults will lead to invalid output streams as data is over- written. */ METHODDEF(boolean) empty_output_buffer (j_compress_ptr cinfo) { mem_dest_ptr dest = (mem_dest_ptr)cinfo->dest; dest->pub.next_output_byte = dest->buffer; dest->pub.free_in_buffer = dest->bufsize; ++dest->errcount; /* need to increase error count */ return TRUE; } /* Usually the library wants to flush output here. I will calculate output buffer size here. Note that results become incorrect, once empty_output_buffer was called. This situation is notified by errcount. */ METHODDEF(void) term_destination (j_compress_ptr cinfo) { mem_dest_ptr dest = (mem_dest_ptr)cinfo->dest; dest->datasize = dest->bufsize - dest->pub.free_in_buffer; if (dest->outsize) *dest->outsize += (int)dest->datasize; } /* Override the default destination manager initialization provided by jpeglib. Since we want to use memory-to-memory compression, we need to use our own destination manager. */ GLOBAL(void) jpeg_memory_dest (j_compress_ptr cinfo, JOCTET* buffer, int bufsize, int* outsize) { mem_dest_ptr dest; /* first call for this instance - need to setup */ if (cinfo->dest == 0) { cinfo->dest = (struct jpeg_destination_mgr *) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, sizeof (memory_destination_mgr)); } dest = (mem_dest_ptr) cinfo->dest; dest->bufsize = bufsize; dest->buffer = buffer; dest->outsize = outsize; /* set method callbacks */ dest->pub.init_destination = init_destination; dest->pub.empty_output_buffer = empty_output_buffer; dest->pub.term_destination = term_destination; } /* ------------------------------------------------------------- */ /* MEMORY SOURCE INTERFACE METHODS */ /* ------------------------------------------------------------- */ /* Called before data is read */ METHODDEF(void) init_source (j_decompress_ptr dinfo) { /* nothing to do here, really. I mean. I'm not lazy or something, but... we're actually through here. */ } /* Called if the decoder wants some bytes that we cannot provide... */ METHODDEF(boolean) fill_input_buffer (j_decompress_ptr dinfo) { /* we can't do anything about this. This might happen if the provided buffer is either invalid with regards to its content or just a to small bufsize has been given. */ /* fail. */ return FALSE; } /* From IJG docs: "it's not clear that being smart is worth much trouble" So I save myself some trouble by ignoring this bit. */ METHODDEF(void) skip_input_data (j_decompress_ptr dinfo, INT32 num_bytes) { /* There might be more data to skip than available in buffer. This clearly is an error, so screw this mess. */ if ((size_t)num_bytes > dinfo->src->bytes_in_buffer) { dinfo->src->next_input_byte = 0; /* no buffer byte */ dinfo->src->bytes_in_buffer = 0; /* no input left */ } else { dinfo->src->next_input_byte += num_bytes; dinfo->src->bytes_in_buffer -= num_bytes; } } /* Finished with decompression */ METHODDEF(void) term_source (j_decompress_ptr dinfo) { /* Again. Absolute laziness. Nothing to do here. Boring. */ } GLOBAL(void) jpeg_memory_src (j_decompress_ptr dinfo, unsigned char* buffer, size_t size) { struct jpeg_source_mgr* src; /* first call for this instance - need to setup */ if (dinfo->src == 0) { dinfo->src = (struct jpeg_source_mgr *) (*dinfo->mem->alloc_small) ((j_common_ptr) dinfo, JPOOL_PERMANENT, sizeof (struct jpeg_source_mgr)); } src = dinfo->src; src->next_input_byte = buffer; src->bytes_in_buffer = size; src->init_source = init_source; src->fill_input_buffer = fill_input_buffer; src->skip_input_data = skip_input_data; src->term_source = term_source; /* IJG recommend to use their function - as I don't know **** about how to do better, I follow this recommendation */ src->resync_to_restart = jpeg_resync_to_restart; } </code></pre> And in your main compression function replace the jpeg_stdio_dest with <pre><code>int numBytes = 0; //size of jpeg after compression char * storage = new char[150000]; //storage buffer JOCTET *jpgbuff = (JOCTET*)storage; //JOCTET pointer to buffer jpeg_memory_dest(&cinfo,jpgbuff,150000,&numBytes); </code></pre> The 150000 is a static size buffer, you probably will have images that will exceed it, so allocate accordingly.
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