Java example source code file (jpegdecoder.c)
The jpegdecoder.c Java example source code
/*
* Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* This file was based upon the example.c stub file included in the
* release 6 of the Independent JPEG Group's free JPEG software.
* It has been updated to conform to release 6b.
*/
/* First, if system header files define "boolean" map it to "system_boolean" */
#define boolean system_boolean
#include <stdio.h>
#include <setjmp.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include "jni.h"
#include "jni_util.h"
/* undo "system_boolean" hack and undef FAR since we don't use it anyway */
#undef boolean
#undef FAR
#include <jpeglib.h>
#include "jerror.h"
/* The method IDs we cache. Note that the last two belongs to the
* java.io.InputStream class.
*/
static jmethodID sendHeaderInfoID;
static jmethodID sendPixelsByteID;
static jmethodID sendPixelsIntID;
static jmethodID InputStream_readID;
static jmethodID InputStream_availableID;
/* Initialize the Java VM instance variable when the library is
first loaded */
JavaVM *jvm;
JNIEXPORT jint JNICALL
JNI_OnLoad(JavaVM *vm, void *reserved)
{
jvm = vm;
return JNI_VERSION_1_2;
}
/*
* ERROR HANDLING:
*
* The JPEG library's standard error handler (jerror.c) is divided into
* several "methods" which you can override individually. This lets you
* adjust the behavior without duplicating a lot of code, which you might
* have to update with each future release.
*
* Our example here shows how to override the "error_exit" method so that
* control is returned to the library's caller when a fatal error occurs,
* rather than calling exit() as the standard error_exit method does.
*
* We use C's setjmp/longjmp facility to return control. This means that the
* routine which calls the JPEG library must first execute a setjmp() call to
* establish the return point. We want the replacement error_exit to do a
* longjmp(). But we need to make the setjmp buffer accessible to the
* error_exit routine. To do this, we make a private extension of the
* standard JPEG error handler object. (If we were using C++, we'd say we
* were making a subclass of the regular error handler.)
*
* Here's the extended error handler struct:
*/
struct sun_jpeg_error_mgr {
struct jpeg_error_mgr pub; /* "public" fields */
jmp_buf setjmp_buffer; /* for return to caller */
};
typedef struct sun_jpeg_error_mgr * sun_jpeg_error_ptr;
/*
* Here's the routine that will replace the standard error_exit method:
*/
METHODDEF(void)
sun_jpeg_error_exit (j_common_ptr cinfo)
{
/* cinfo->err really points to a sun_jpeg_error_mgr struct */
sun_jpeg_error_ptr myerr = (sun_jpeg_error_ptr) cinfo->err;
/* Always display the message. */
/* We could postpone this until after returning, if we chose. */
/* (*cinfo->err->output_message) (cinfo); */
/* For Java, we will format the message and put it in the error we throw. */
/* Return control to the setjmp point */
longjmp(myerr->setjmp_buffer, 1);
}
/*
* Error Message handling
*
* This overrides the output_message method to send JPEG messages
*
*/
METHODDEF(void)
sun_jpeg_output_message (j_common_ptr cinfo)
{
char buffer[JMSG_LENGTH_MAX];
/* Create the message */
(*cinfo->err->format_message) (cinfo, buffer);
/* Send it to stderr, adding a newline */
fprintf(stderr, "%s\n", buffer);
}
/*
* INPUT HANDLING:
*
* The JPEG library's input management is defined by the jpeg_source_mgr
* structure which contains two fields to convey the information in the
* buffer and 5 methods which perform all buffer management. The library
* defines a standard input manager that uses stdio for obtaining compressed
* jpeg data, but here we need to use Java to get our data.
*
* We need to make the Java class information accessible to the source_mgr
* input routines. We also need to store a pointer to the start of the
* Java array being used as an input buffer so that it is not moved or
* garbage collected while the JPEG library is using it. To store these
* things, we make a private extension of the standard JPEG jpeg_source_mgr
* object.
*
* Here's the extended source manager struct:
*/
struct sun_jpeg_source_mgr {
struct jpeg_source_mgr pub; /* "public" fields */
jobject hInputStream;
int suspendable;
unsigned long remaining_skip;
JOCTET *inbuf;
jbyteArray hInputBuffer;
size_t inbufoffset;
/* More stuff */
union pixptr {
int *ip;
unsigned char *bp;
} outbuf;
jobject hOutputBuffer;
};
typedef struct sun_jpeg_source_mgr * sun_jpeg_source_ptr;
/* We use Get/ReleasePrimitiveArrayCritical functions to avoid
* the need to copy buffer elements.
*
* MAKE SURE TO:
*
* - carefully insert pairs of RELEASE_ARRAYS and GET_ARRAYS around
* callbacks to Java.
* - call RELEASE_ARRAYS before returning to Java.
*
* Otherwise things will go horribly wrong. There may be memory leaks,
* excessive pinning, or even VM crashes!
*
* Note that GetPrimitiveArrayCritical may fail!
*/
static void RELEASE_ARRAYS(JNIEnv *env, sun_jpeg_source_ptr src)
{
if (src->inbuf) {
if (src->pub.next_input_byte == 0) {
src->inbufoffset = -1;
} else {
src->inbufoffset = src->pub.next_input_byte - src->inbuf;
}
(*env)->ReleasePrimitiveArrayCritical(env, src->hInputBuffer,
src->inbuf, 0);
src->inbuf = 0;
}
if (src->outbuf.ip) {
(*env)->ReleasePrimitiveArrayCritical(env, src->hOutputBuffer,
src->outbuf.ip, 0);
src->outbuf.ip = 0;
}
}
static int GET_ARRAYS(JNIEnv *env, sun_jpeg_source_ptr src)
{
if (src->hInputBuffer) {
assert(src->inbuf == 0);
src->inbuf = (JOCTET *)(*env)->GetPrimitiveArrayCritical
(env, src->hInputBuffer, 0);
if (src->inbuf == 0) {
return 0;
}
if ((int)(src->inbufoffset) >= 0) {
src->pub.next_input_byte = src->inbuf + src->inbufoffset;
}
}
if (src->hOutputBuffer) {
assert(src->outbuf.ip == 0);
src->outbuf.ip = (int *)(*env)->GetPrimitiveArrayCritical
(env, src->hOutputBuffer, 0);
if (src->outbuf.ip == 0) {
RELEASE_ARRAYS(env, src);
return 0;
}
}
return 1;
}
/*
* Initialize source. This is called by jpeg_read_header() before any
* data is actually read. Unlike init_destination(), it may leave
* bytes_in_buffer set to 0 (in which case a fill_input_buffer() call
* will occur immediately).
*/
GLOBAL(void)
sun_jpeg_init_source(j_decompress_ptr cinfo)
{
sun_jpeg_source_ptr src = (sun_jpeg_source_ptr) cinfo->src;
src->pub.next_input_byte = 0;
src->pub.bytes_in_buffer = 0;
}
/*
* This is called whenever bytes_in_buffer has reached zero and more
* data is wanted. In typical applications, it should read fresh data
* into the buffer (ignoring the current state of next_input_byte and
* bytes_in_buffer), reset the pointer & count to the start of the
* buffer, and return TRUE indicating that the buffer has been reloaded.
* It is not necessary to fill the buffer entirely, only to obtain at
* least one more byte. bytes_in_buffer MUST be set to a positive value
* if TRUE is returned. A FALSE return should only be used when I/O
* suspension is desired (this mode is discussed in the next section).
*/
/*
* Note that with I/O suspension turned on, this procedure should not
* do any work since the JPEG library has a very simple backtracking
* mechanism which relies on the fact that the buffer will be filled
* only when it has backed out to the top application level. When
* suspendable is turned on, the sun_jpeg_fill_suspended_buffer will
* do the actual work of filling the buffer.
*/
GLOBAL(boolean)
sun_jpeg_fill_input_buffer(j_decompress_ptr cinfo)
{
sun_jpeg_source_ptr src = (sun_jpeg_source_ptr) cinfo->src;
JNIEnv *env = (JNIEnv *)JNU_GetEnv(jvm, JNI_VERSION_1_2);
int ret, buflen;
if (src->suspendable) {
return FALSE;
}
if (src->remaining_skip) {
src->pub.skip_input_data(cinfo, 0);
}
RELEASE_ARRAYS(env, src);
buflen = (*env)->GetArrayLength(env, src->hInputBuffer);
ret = (*env)->CallIntMethod(env, src->hInputStream, InputStream_readID,
src->hInputBuffer, 0, buflen);
if ((*env)->ExceptionOccurred(env) || !GET_ARRAYS(env, src)) {
cinfo->err->error_exit((struct jpeg_common_struct *) cinfo);
}
if (ret <= 0) {
/* Silently accept truncated JPEG files */
WARNMS(cinfo, JWRN_JPEG_EOF);
src->inbuf[0] = (JOCTET) 0xFF;
src->inbuf[1] = (JOCTET) JPEG_EOI;
ret = 2;
}
src->pub.next_input_byte = src->inbuf;
src->pub.bytes_in_buffer = ret;
return TRUE;
}
/*
* Note that with I/O suspension turned on, the JPEG library requires
* that all buffer filling be done at the top application level. Due
* to the way that backtracking works, this procedure should save all
* of the data that was left in the buffer when suspension occurred and
* only read new data at the end.
*/
GLOBAL(void)
sun_jpeg_fill_suspended_buffer(j_decompress_ptr cinfo)
{
sun_jpeg_source_ptr src = (sun_jpeg_source_ptr) cinfo->src;
JNIEnv *env = (JNIEnv *)JNU_GetEnv(jvm, JNI_VERSION_1_2);
size_t offset, buflen;
int ret;
RELEASE_ARRAYS(env, src);
ret = (*env)->CallIntMethod(env, src->hInputStream,
InputStream_availableID);
if ((*env)->ExceptionOccurred(env) || !GET_ARRAYS(env, src)) {
cinfo->err->error_exit((struct jpeg_common_struct *) cinfo);
}
if (ret < 0 || (unsigned int)ret <= src->remaining_skip) {
return;
}
if (src->remaining_skip) {
src->pub.skip_input_data(cinfo, 0);
}
/* Save the data currently in the buffer */
offset = src->pub.bytes_in_buffer;
if (src->pub.next_input_byte > src->inbuf) {
memmove(src->inbuf, src->pub.next_input_byte, offset);
}
RELEASE_ARRAYS(env, src);
buflen = (*env)->GetArrayLength(env, src->hInputBuffer) - offset;
if (buflen <= 0) {
if (!GET_ARRAYS(env, src)) {
cinfo->err->error_exit((struct jpeg_common_struct *) cinfo);
}
return;
}
ret = (*env)->CallIntMethod(env, src->hInputStream, InputStream_readID,
src->hInputBuffer, offset, buflen);
if ((*env)->ExceptionOccurred(env) || !GET_ARRAYS(env, src)) {
cinfo->err->error_exit((struct jpeg_common_struct *) cinfo);
}
if (ret <= 0) {
/* Silently accept truncated JPEG files */
WARNMS(cinfo, JWRN_JPEG_EOF);
src->inbuf[offset] = (JOCTET) 0xFF;
src->inbuf[offset + 1] = (JOCTET) JPEG_EOI;
ret = 2;
}
src->pub.next_input_byte = src->inbuf;
src->pub.bytes_in_buffer = ret + offset;
return;
}
/*
* Skip num_bytes worth of data. The buffer pointer and count should
* be advanced over num_bytes input bytes, refilling the buffer as
* needed. This is used to skip over a potentially large amount of
* uninteresting data (such as an APPn marker). In some applications
* it may be possible to optimize away the reading of the skipped data,
* but it's not clear that being smart is worth much trouble; large
* skips are uncommon. bytes_in_buffer may be zero on return.
* A zero or negative skip count should be treated as a no-op.
*/
/*
* Note that with I/O suspension turned on, this procedure should not
* do any I/O since the JPEG library has a very simple backtracking
* mechanism which relies on the fact that the buffer will be filled
* only when it has backed out to the top application level.
*/
GLOBAL(void)
sun_jpeg_skip_input_data(j_decompress_ptr cinfo, long num_bytes)
{
sun_jpeg_source_ptr src = (sun_jpeg_source_ptr) cinfo->src;
JNIEnv *env = (JNIEnv *)JNU_GetEnv(jvm, JNI_VERSION_1_2);
int ret;
int buflen;
if (num_bytes < 0) {
return;
}
num_bytes += src->remaining_skip;
src->remaining_skip = 0;
ret = (int)src->pub.bytes_in_buffer; /* this conversion is safe, because capacity of the buffer is limited by jnit */
if (ret >= num_bytes) {
src->pub.next_input_byte += num_bytes;
src->pub.bytes_in_buffer -= num_bytes;
return;
}
num_bytes -= ret;
if (src->suspendable) {
src->remaining_skip = num_bytes;
src->pub.bytes_in_buffer = 0;
src->pub.next_input_byte = src->inbuf;
return;
}
/* Note that the signature for the method indicates that it takes
* and returns a long. Casting the int num_bytes to a long on
* the input should work well enough, and if we assume that the
* return value for this particular method should always be less
* than the argument value (or -1), then the return value coerced
* to an int should return us the information we need...
*/
RELEASE_ARRAYS(env, src);
buflen = (*env)->GetArrayLength(env, src->hInputBuffer);
while (num_bytes > 0) {
ret = (*env)->CallIntMethod(env, src->hInputStream,
InputStream_readID,
src->hInputBuffer, 0, buflen);
if ((*env)->ExceptionOccurred(env)) {
cinfo->err->error_exit((struct jpeg_common_struct *) cinfo);
}
if (ret < 0) {
break;
}
num_bytes -= ret;
}
if (!GET_ARRAYS(env, src)) {
cinfo->err->error_exit((struct jpeg_common_struct *) cinfo);
}
if (num_bytes > 0) {
/* Silently accept truncated JPEG files */
WARNMS(cinfo, JWRN_JPEG_EOF);
src->inbuf[0] = (JOCTET) 0xFF;
src->inbuf[1] = (JOCTET) JPEG_EOI;
src->pub.bytes_in_buffer = 2;
src->pub.next_input_byte = src->inbuf;
} else {
src->pub.bytes_in_buffer = -num_bytes;
src->pub.next_input_byte = src->inbuf + ret + num_bytes;
}
}
/*
* Terminate source --- called by jpeg_finish_decompress() after all
* data has been read. Often a no-op.
*/
GLOBAL(void)
sun_jpeg_term_source(j_decompress_ptr cinfo)
{
}
JNIEXPORT void JNICALL
Java_sun_awt_image_JPEGImageDecoder_initIDs(JNIEnv *env, jclass cls,
jclass InputStreamClass)
{
sendHeaderInfoID = (*env)->GetMethodID(env, cls, "sendHeaderInfo",
"(IIZZZ)Z");
sendPixelsByteID = (*env)->GetMethodID(env, cls, "sendPixels", "([BI)Z");
sendPixelsIntID = (*env)->GetMethodID(env, cls, "sendPixels", "([II)Z");
InputStream_readID = (*env)->GetMethodID(env, InputStreamClass,
"read", "([BII)I");
InputStream_availableID = (*env)->GetMethodID(env, InputStreamClass,
"available", "()I");
}
/*
* The Windows Itanium Aug 2002 SDK generates bad code
* for this routine. Disable optimization for now.
*/
#ifdef _M_IA64
#pragma optimize ("", off)
#endif
JNIEXPORT void JNICALL
Java_sun_awt_image_JPEGImageDecoder_readImage(JNIEnv *env,
jobject this,
jobject hInputStream,
jbyteArray hInputBuffer)
{
/* This struct contains the JPEG decompression parameters and pointers to
* working space (which is allocated as needed by the JPEG library).
*/
struct jpeg_decompress_struct cinfo;
/* We use our private extension JPEG error handler.
* Note that this struct must live as long as the main JPEG parameter
* struct, to avoid dangling-pointer problems.
*/
struct sun_jpeg_error_mgr jerr;
struct sun_jpeg_source_mgr jsrc;
int ret;
unsigned char *bp;
int *ip, pixel;
int grayscale;
int hasalpha;
int buffered_mode;
int final_pass;
/* Step 0: verify the inputs. */
if (hInputBuffer == 0 || hInputStream == 0) {
JNU_ThrowNullPointerException(env, 0);
return;
}
jsrc.outbuf.ip = 0;
jsrc.inbuf = 0;
/* Step 1: allocate and initialize JPEG decompression object */
/* We set up the normal JPEG error routines, then override error_exit. */
cinfo.err = jpeg_std_error(&jerr.pub);
jerr.pub.error_exit = sun_jpeg_error_exit;
/* We need to setup our own print routines */
jerr.pub.output_message = sun_jpeg_output_message;
/* Establish the setjmp return context for sun_jpeg_error_exit to use. */
if (setjmp(jerr.setjmp_buffer)) {
/* If we get here, the JPEG code has signaled an error.
* We need to clean up the JPEG object, close the input file, and return.
*/
jpeg_destroy_decompress(&cinfo);
RELEASE_ARRAYS(env, &jsrc);
if (!(*env)->ExceptionOccurred(env)) {
char buffer[JMSG_LENGTH_MAX];
(*cinfo.err->format_message) ((struct jpeg_common_struct *) &cinfo,
buffer);
JNU_ThrowByName(env, "sun/awt/image/ImageFormatException", buffer);
}
return;
}
/* Now we can initialize the JPEG decompression object. */
jpeg_create_decompress(&cinfo);
/* Step 2: specify data source (eg, a file) */
cinfo.src = &jsrc.pub;
jsrc.hInputStream = hInputStream;
jsrc.hInputBuffer = hInputBuffer;
jsrc.hOutputBuffer = 0;
jsrc.suspendable = FALSE;
jsrc.remaining_skip = 0;
jsrc.inbufoffset = -1;
jsrc.pub.init_source = sun_jpeg_init_source;
jsrc.pub.fill_input_buffer = sun_jpeg_fill_input_buffer;
jsrc.pub.skip_input_data = sun_jpeg_skip_input_data;
jsrc.pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
jsrc.pub.term_source = sun_jpeg_term_source;
if (!GET_ARRAYS(env, &jsrc)) {
jpeg_destroy_decompress(&cinfo);
return;
}
/* Step 3: read file parameters with jpeg_read_header() */
(void) jpeg_read_header(&cinfo, TRUE);
/* select buffered-image mode if it is a progressive JPEG only */
buffered_mode = cinfo.buffered_image = jpeg_has_multiple_scans(&cinfo);
grayscale = (cinfo.out_color_space == JCS_GRAYSCALE);
#ifdef YCCALPHA
hasalpha = (cinfo.out_color_space == JCS_RGBA);
#else
hasalpha = 0;
#endif
/* We can ignore the return value from jpeg_read_header since
* (a) suspension is not possible with the stdio data source, and
* (nor with the Java input source)
* (b) we passed TRUE to reject a tables-only JPEG file as an error.
* See libjpeg.doc for more info.
*/
RELEASE_ARRAYS(env, &jsrc);
ret = (*env)->CallBooleanMethod(env, this, sendHeaderInfoID,
cinfo.image_width, cinfo.image_height,
grayscale, hasalpha, buffered_mode);
if ((*env)->ExceptionOccurred(env) || !ret) {
/* No more interest in this image... */
jpeg_destroy_decompress(&cinfo);
return;
}
/* Make a one-row-high sample array with enough room to expand to ints */
if (grayscale) {
jsrc.hOutputBuffer = (*env)->NewByteArray(env, cinfo.image_width);
} else {
jsrc.hOutputBuffer = (*env)->NewIntArray(env, cinfo.image_width);
}
if (jsrc.hOutputBuffer == 0 || !GET_ARRAYS(env, &jsrc)) {
jpeg_destroy_decompress(&cinfo);
return;
}
/* Step 4: set parameters for decompression */
/* In this example, we don't need to change any of the defaults set by
* jpeg_read_header(), so we do nothing here.
*/
/* For the first pass for Java, we want to deal with RGB for simplicity */
/* Unfortunately, the JPEG code does not automatically convert Grayscale */
/* to RGB, so we have to deal with Grayscale explicitly. */
if (!grayscale && !hasalpha) {
cinfo.out_color_space = JCS_RGB;
}
/* Step 5: Start decompressor */
jpeg_start_decompress(&cinfo);
/* We may need to do some setup of our own at this point before reading
* the data. After jpeg_start_decompress() we have the correct scaled
* output image dimensions available, as well as the output colormap
* if we asked for color quantization.
*/
/* Step 6: while (scan lines remain to be read) */
/* jpeg_read_scanlines(...); */
/* Here we use the library's state variable cinfo.output_scanline as the
* loop counter, so that we don't have to keep track ourselves.
*/
if (buffered_mode) {
final_pass = FALSE;
cinfo.dct_method = JDCT_IFAST;
} else {
final_pass = TRUE;
}
do {
if (buffered_mode) {
do {
sun_jpeg_fill_suspended_buffer(&cinfo);
jsrc.suspendable = TRUE;
ret = jpeg_consume_input(&cinfo);
jsrc.suspendable = FALSE;
} while (ret != JPEG_SUSPENDED && ret != JPEG_REACHED_EOI);
if (ret == JPEG_REACHED_EOI) {
final_pass = TRUE;
cinfo.dct_method = JDCT_ISLOW;
}
jpeg_start_output(&cinfo, cinfo.input_scan_number);
}
while (cinfo.output_scanline < cinfo.output_height) {
if (! final_pass) {
do {
sun_jpeg_fill_suspended_buffer(&cinfo);
jsrc.suspendable = TRUE;
ret = jpeg_consume_input(&cinfo);
jsrc.suspendable = FALSE;
} while (ret != JPEG_SUSPENDED && ret != JPEG_REACHED_EOI);
if (ret == JPEG_REACHED_EOI) {
break;
}
}
(void) jpeg_read_scanlines(&cinfo, (JSAMPARRAY) &(jsrc.outbuf), 1);
if (grayscale) {
RELEASE_ARRAYS(env, &jsrc);
ret = (*env)->CallBooleanMethod(env, this, sendPixelsByteID,
jsrc.hOutputBuffer,
cinfo.output_scanline - 1);
} else {
if (hasalpha) {
ip = jsrc.outbuf.ip + cinfo.image_width;
bp = jsrc.outbuf.bp + cinfo.image_width * 4;
while (ip > jsrc.outbuf.ip) {
pixel = (*--bp) << 24;
pixel |= (*--bp);
pixel |= (*--bp) << 8;
pixel |= (*--bp) << 16;
*--ip = pixel;
}
} else {
ip = jsrc.outbuf.ip + cinfo.image_width;
bp = jsrc.outbuf.bp + cinfo.image_width * 3;
while (ip > jsrc.outbuf.ip) {
pixel = (*--bp);
pixel |= (*--bp) << 8;
pixel |= (*--bp) << 16;
*--ip = pixel;
}
}
RELEASE_ARRAYS(env, &jsrc);
ret = (*env)->CallBooleanMethod(env, this, sendPixelsIntID,
jsrc.hOutputBuffer,
cinfo.output_scanline - 1);
}
if ((*env)->ExceptionOccurred(env) || !ret ||
!GET_ARRAYS(env, &jsrc)) {
/* No more interest in this image... */
jpeg_destroy_decompress(&cinfo);
return;
}
}
if (buffered_mode) {
jpeg_finish_output(&cinfo);
}
} while (! final_pass);
/* Step 7: Finish decompression */
(void) jpeg_finish_decompress(&cinfo);
/* We can ignore the return value since suspension is not possible
* with the stdio data source.
* (nor with the Java data source)
*/
/* Step 8: Release JPEG decompression object */
/* This is an important step since it will release a good deal of memory. */
jpeg_destroy_decompress(&cinfo);
/* After finish_decompress, we can close the input file.
* Here we postpone it until after no more JPEG errors are possible,
* so as to simplify the setjmp error logic above. (Actually, I don't
* think that jpeg_destroy can do an error exit, but why assume anything...)
*/
/* Not needed for Java - the Java code will close the file */
/* fclose(infile); */
/* At this point you may want to check to see whether any corrupt-data
* warnings occurred (test whether jerr.pub.num_warnings is nonzero).
*/
/* And we're done! */
RELEASE_ARRAYS(env, &jsrc);
return;
}
#ifdef _M_IA64
#pragma optimize ("", on)
#endif
/*
* SOME FINE POINTS:
*
* In the above code, we ignored the return value of jpeg_read_scanlines,
* which is the number of scanlines actually read. We could get away with
* this because we asked for only one line at a time and we weren't using
* a suspending data source. See libjpeg.doc for more info.
*
* We cheated a bit by calling alloc_sarray() after jpeg_start_decompress();
* we should have done it beforehand to ensure that the space would be
* counted against the JPEG max_memory setting. In some systems the above
* code would risk an out-of-memory error. However, in general we don't
* know the output image dimensions before jpeg_start_decompress(), unless we
* call jpeg_calc_output_dimensions(). See libjpeg.doc for more about this.
*
* Scanlines are returned in the same order as they appear in the JPEG file,
* which is standardly top-to-bottom. If you must emit data bottom-to-top,
* you can use one of the virtual arrays provided by the JPEG memory manager
* to invert the data. See wrbmp.c for an example.
*
* As with compression, some operating modes may require temporary files.
* On some systems you may need to set up a signal handler to ensure that
* temporary files are deleted if the program is interrupted. See libjpeg.doc.
*/
Other Java examples (source code examples)Here is a short list of links related to this Java jpegdecoder.c source code file: |
The search page
Other Java source code examples at this package level
Click here to learn more about this project
