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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>JPEG IO</title><link rel="stylesheet" type="text/css" href="../styles/main.css"><script language=JavaScript src="../javascript/main.js"></script><script language=JavaScript src="../javascript/prettify.js"></script><script language=JavaScript src="../javascript/searchdata.js"></script></head><body class="ContentPage" onLoad="NDOnLoad();prettyPrint();"><script language=JavaScript>
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if (browserType) {document.write("
");if (browserVer) {document.write("
"); }}// --></script>
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JPEG IO
Read and write JPEG images.
Summary
JPEG IORead and write JPEG images.
Functions
gdImageJpeggdImageJpeg outputs the specified image to the specified file in JPEG format. 
gdImageJpegPtrIdentical to gdImageJpeg except that it returns a pointer to a memory area with the JPEG data. 
gdImageJpegCtxWrite the image as JPEG data via a gdIOCtx. 
gdImageCreateFromJpegSee gdImageCreateFromJpegEx.
gdImageCreateFromJpegExgdImageCreateFromJpegEx is called to load truecolor images from JPEG format files. 
gdImageCreateFromJpegPtr
gdImageCreateFromJpegPtrEx
gdImageCreateFromJpegCtxSee gdImageCreateFromJpeg.
gdImageCreateFromJpegCtxExSee gdImageCreateFromJpeg.
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Functions
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gdImageJpeg
void gdImageJpeg(gdImagePtr im,
FILE *outFile,
int quality)
gdImageJpeg outputs the specified image to the specified file in JPEG format.  The file must be open for writing.  Under MSDOS and all versions of Windows, it is important to use “wb” as opposed to simply “w” as the mode when opening the file, and under Unix there is no penalty for doing so.  gdImageJpeg does not close the file; your code must do so.
If <u>quality</u> is negative, the default IJG JPEG quality value (which should yield a good general quality / size tradeoff for most situations) is used.  Otherwise, for practical purposes, <u>quality</u> should be a value in the range 0-95, higher quality values usually implying both higher quality and larger image sizes.
If you have set image interlacing using gdImageInterlace, this function will interpret that to mean you wish to output a progressive JPEG.  Some programs (e.g., Web browsers) can display progressive JPEGs incrementally; this can be useful when browsing over a relatively slow communications link, for example.  Progressive JPEGs can also be slightly smaller than sequential (non-progressive) JPEGs.
Variants
gdImageJpegCtx stores the image using a gdIOCtx struct.
gdImageJpegPtr stores the image to RAM.
Parameters
imThe image to save
outFileThe FILE pointer to write to.
qualityCompression quality (0-95, 0 means use the default).
Returns
Nothing.
Example
gdImagePtr im;
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int black, white;
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FILE *out;
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// Create the image
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im = gdImageCreate(100, 100);
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// Allocate background
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white = gdImageColorAllocate(im, 255, 255, 255);
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// Allocate drawing color
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black = gdImageColorAllocate(im, 0, 0, 0);
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// Draw rectangle
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gdImageRectangle(im, 0, 0, 99, 99, black);
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// Open output file in binary mode
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out = fopen("rect.jpg", "wb");
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// Write JPEG using default quality
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gdImageJpeg(im, out, -1);
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// Close file
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fclose(out);
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// Destroy image
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gdImageDestroy(im);
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gdImageJpegPtr
void * gdImageJpegPtr(gdImagePtr im,
int *size,
int quality)
Identical to gdImageJpeg except that it returns a pointer to a memory area with the JPEG data.  This memory must be freed by the caller when it is no longer needed.
The caller must invoke gdFree, not free().   This is because it is not guaranteed that libgd will use the same implementation of malloc, free, etc. as your proggram.
The ‘size’ parameter receives the total size of the block of memory.
Parameters
imThe image to write
sizeOutput: the size of the resulting image.
qualityCompression quality.
Returns
A pointer to the JPEG data or NULL if an error occurred.
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gdImageJpegCtx
void gdImageJpegCtx(gdImagePtr im,
gdIOCtx *outfile,
int quality)
Write the image as JPEG data via a gdIOCtx.  See gdImageJpeg for more details.
Parameters
imThe image to write.
outfileThe output sink.
qualityImage quality.
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gdImageCreateFromJpeg
gdImagePtr gdImageCreateFromJpeg(FILE *inFile)
See gdImageCreateFromJpegEx.
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gdImageCreateFromJpegEx
gdImagePtr gdImageCreateFromJpegEx(FILE *inFile,
int ignore_warning)
gdImageCreateFromJpegEx is called to load truecolor images from JPEG format files.  Invoke gdImageCreateFromJpegEx with an already opened pointer to a file containing the desired image.  gdImageCreateFromJpegEx returns a gdImagePtr to the new truecolor image, or NULL if unable to load the image (most often because the file is corrupt or does not contain a JPEG image).  gdImageCreateFromJpegEx does not close the file.
You can inspect the sx and sy members of the image to determine its size.  The image must eventually be destroyed using gdImageDestroy.
The returned image is always a truecolor image.
Variants
gdImageCreateFromJpegPtrEx creates an image from JPEG data already in memory.
gdImageCreateFromJpegCtxEx reads its data via the function pointers in a gdIOCtx structure.
gdImageCreateFromJpeg, gdImageCreateFromJpegPtr and gdImageCreateFromJpegCtx are equivalent to calling their <u>Ex</u>-named counterparts with an ignore_warning set to 1 (i.e.  TRUE).
Parameters
infileThe input FILE pointer.
ignore_warningFlag.   If true, ignores recoverable warnings.
Returns
A pointer to the new truecolor image.   This will need to be destroyed with gdImageDestroy once it is no longer needed.
On error, returns NULL.
Example
gdImagePtr im;
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FILE *in;
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in = fopen("myjpeg.jpg", "rb");
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im = gdImageCreateFromJpegEx(in, GD_TRUE);
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fclose(in);
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// ... Use the image ...
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gdImageDestroy(im);
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gdImageCreateFromJpegPtr
gdImagePtr gdImageCreateFromJpegPtr(int size,
void *data)
Parameters
sizesize of JPEG data in bytes.
datapointer to JPEG data.
See gdImageCreateFromJpegEx.
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gdImageCreateFromJpegPtrEx
gdImagePtr gdImageCreateFromJpegPtrEx(int size,
void *data,
int ignore_warning)
Parameters
sizesize of JPEG data in bytes.
datapointer to JPEG data.
ignore_warningif true, ignore recoverable warnings
See gdImageCreateFromJpegEx.
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gdImageCreateFromJpegCtx
gdImagePtr gdImageCreateFromJpegCtx(gdIOCtx *infile)
See gdImageCreateFromJpeg.
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gdImageCreateFromJpegCtxEx
gdImagePtr gdImageCreateFromJpegCtxEx(gdIOCtx *infile,
int ignore_warning)
See gdImageCreateFromJpeg.
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var searchPanel = new SearchPanel("searchPanel", "HTML", "../search");
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--></script>
<input type=text id=MSearchField value=Search onFocus="searchPanel.OnSearchFieldFocus(true)" onBlur="searchPanel.OnSearchFieldFocus(false)" onKeyUp="searchPanel.OnSearchFieldChange()"><select id=MSearchType onFocus="searchPanel.OnSearchTypeFocus(true)" onBlur="searchPanel.OnSearchTypeFocus(false)" onChange="searchPanel.OnSearchTypeChange()"><option  id=MSearchEverything selected value="General">Everything</option><option value="Constants">Constants</option><option value="Files">Files</option><option value="Functions">Functions</option><option value="Macros">Macros</option><option value="Types">Types</option></select>
<script language=JavaScript>
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HideAllBut([1], 4);// --></script>
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void gdImageJpeg(gdImagePtr im,
FILE *outFile,
int quality)
gdImageJpeg outputs the specified image to the specified file in JPEG format. 
void * gdImageJpegPtr(gdImagePtr im,
int *size,
int quality)
Identical to gdImageJpeg except that it returns a pointer to a memory area with the JPEG data. 
void gdImageJpegCtx(gdImagePtr im,
gdIOCtx *outfile,
int quality)
Write the image as JPEG data via a gdIOCtx. 
gdIOCtx structures hold function pointers for doing image IO.
gdImagePtr gdImageCreateFromJpeg(FILE *inFile)
See gdImageCreateFromJpegEx.
gdImagePtr gdImageCreateFromJpegEx(FILE *inFile,
int ignore_warning)
gdImageCreateFromJpegEx is called to load truecolor images from JPEG format files. 
gdImagePtr gdImageCreateFromJpegPtr(int size,
void *data)
gdImagePtr gdImageCreateFromJpegPtrEx(int size,
void *data,
int ignore_warning)
gdImagePtr gdImageCreateFromJpegCtx(gdIOCtx *infile)
See gdImageCreateFromJpeg.
gdImagePtr gdImageCreateFromJpegCtxEx(gdIOCtx *infile,
int ignore_warning)
See gdImageCreateFromJpeg.
void gdImageInterlace (gdImagePtr im,
int interlaceArg)
Sets whether an image is interlaced
void gdFree (void *ptr)
Frees memory that has been allocated by libgd functions.
The data structure in which gd stores images. 
void gdImageDestroy (gdImagePtr im)
gdImageDestroy is used to free the memory associated with an image.
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<script language=JavaScript>
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if (browserType) {if (browserVer) {document.write(""); }document.write("");}// --></script></body></html>

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