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git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@416 632fc199-4ca6-4c93-a231-07263d6284db
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DRC
2011-02-19 17:57:08 +00:00
parent 9cd2c42e84
commit c4c304950d
1 changed files with 19 additions and 19 deletions
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38
turbojpeg.h
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@@ -111,40 +111,40 @@ DLLEXPORT tjhandle DLLCALL tjInitCompress(void);
[INPUT] j = instance handle previously returned from a call to
tjInitCompress()
[INPUT] srcbuf = pointer to user-allocated image buffer containing pixels in
RGB(A) or BGR(A) form
[INPUT] srcbuf = pointer to user-allocated image buffer containing RGB or
grayscale pixels to be compressed
[INPUT] width = width (in pixels) of the source image
[INPUT] pitch = bytes per line of the source image (width*pixelsize if the
bitmap is unpadded, else TJPAD(width*pixelsize) if each line of the bitmap
is padded to the nearest 32-bit boundary, such as is the case for Windows
bitmaps. You can also be clever and use this parameter to skip lines,
etc. Setting this parameter to 0 is the equivalent of setting it to
width*pixelsize;
width*pixelsize.
[INPUT] height = height (in pixels) of the source image
[INPUT] pixelsize = size (in bytes) of each pixel in the source image
RGBA and BGRA: 4, RGB and BGR: 3, Grayscale: 1
RGBX/BGRX/XRGB/XBGR: 4, RGB/BGR: 3, Grayscale: 1
[INPUT] dstbuf = pointer to user-allocated image buffer which will receive
the JPEG image. Use the macro TJBUFSIZE(width, height) to determine
the JPEG image. Use the TJBUFSIZE(width, height) function to determine
the appropriate size for this buffer based on the image width and height.
[OUTPUT] size = pointer to unsigned long which receives the size (in bytes)
of the compressed image
[INPUT] jpegsubsamp = Specifies either 4:2:0, 4:2:2, or 4:4:4 subsampling.
When the image is converted from the RGB to YCbCr colorspace as part of the
JPEG compression process, every other Cb and Cr (chrominance) pixel can be
discarded to produce a smaller image with little perceptible loss of
image clarity (the human eye is more sensitive to small changes in
When the image is converted from the RGB to YCbCr colorspace as part of
the JPEG compression process, every other Cb and Cr (chrominance) pixel
can be discarded to produce a smaller image with little perceptible loss
of image clarity (the human eye is more sensitive to small changes in
brightness than small changes in color.)
TJ_420: 4:2:0 subsampling. Discards every other Cb, Cr pixel in both
horizontal and vertical directions.
horizontal and vertical directions
TJ_422: 4:2:2 subsampling. Discards every other Cb, Cr pixel only in
the horizontal direction.
TJ_444: no subsampling.
the horizontal direction
TJ_444: no subsampling
TJ_GRAYSCALE: Generate grayscale JPEG image
[INPUT] jpegqual = JPEG quality (an integer between 0 and 100 inclusive.)
[INPUT] jpegqual = JPEG quality (an integer between 0 and 100 inclusive)
[INPUT] flags = the bitwise OR of one or more of the flags described in the
"Flags" section above.
"Flags" section above
RETURNS: 0 on success, -1 on error
*/
@@ -172,7 +172,7 @@ DLLEXPORT tjhandle DLLCALL tjInitDecompress(void);
/*
int tjDecompressHeader2(tjhandle j,
unsigned char *srcbuf, unsigned long size,
int *width, int *height, int *jpegsub)
int *width, int *height, int *jpegsubsamp)
[INPUT] j = instance handle previously returned from a call to
tjInitDecompress()
@@ -181,14 +181,14 @@ DLLEXPORT tjhandle DLLCALL tjInitDecompress(void);
[INPUT] size = size of the JPEG image buffer (in bytes)
[OUTPUT] width = width (in pixels) of the JPEG image
[OUTPUT] height = height (in pixels) of the JPEG image
[OUTPUT] jpegsub = type of chrominance subsampling used when compressing the
JPEG image
[OUTPUT] jpegsubsamp = type of chrominance subsampling used when compressing
the JPEG image
RETURNS: 0 on success, -1 on error
*/
DLLEXPORT int DLLCALL tjDecompressHeader2(tjhandle j,
unsigned char *srcbuf, unsigned long size,
int *width, int *height, int *jpegsub);
int *width, int *height, int *jpegsubsamp);
/*
Legacy version of the above function
@@ -222,7 +222,7 @@ DLLEXPORT int DLLCALL tjDecompressHeader(tjhandle j,
clever and use this parameter to skip lines, etc. Setting this parameter
to 0 is the equivalent of setting it to scaled_width*pixelsize.
[INPUT] pixelsize = size (in bytes) of each pixel in the destination image
RGBA/RGBx and BGRA/BGRx: 4, RGB and BGR: 3, Grayscale: 1
RGBX/BGRX/XRGB/XBGR: 4, RGB/BGR: 3, Grayscale: 1
[INPUT] scale_num = numerator of scaling factor (currently must be 1)
[INPUT] scale_denom = denominator of scaling factor (1, 2, 4, or 8)
[INPUT] flags = the bitwise OR of one or more of the flags described in the