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Jules Maselbas
parent
c04a975e00
commit
b060b961e8
94
qoi.h
94
qoi.h
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@ -28,8 +28,8 @@ SOFTWARE.
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-- About
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QOI encodes and decodes images in a lossless format. Compared to stb_image and
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stb_image_write QOI offers 20x-50x faster encoding, 3x-4x faster decoding and
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QOI encodes and decodes images in a lossless format. Compared to stb_image and
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stb_image_write QOI offers 20x-50x faster encoding, 3x-4x faster decoding and
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20% better compression.
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@ -45,7 +45,7 @@ stb_image_write QOI offers 20x-50x faster encoding, 3x-4x faster decoding and
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// the input pixel data.
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qoi_write("image_new.qoi", rgba_pixels, &(qoi_desc){
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.width = 1920,
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.height = 1080,
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.height = 1080,
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.channels = 4,
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.colorspace = QOI_SRGB
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});
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@ -74,7 +74,7 @@ QOI_NO_STDIO before including this library.
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This library uses malloc() and free(). To supply your own malloc implementation
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you can define QOI_MALLOC and QOI_FREE before including this library.
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This library uses memset() to zero-initialize the index. To supply your own
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This library uses memset() to zero-initialize the index. To supply your own
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implementation you can define QOI_ZEROARR before including this library.
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@ -91,8 +91,8 @@ struct qoi_header_t {
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uint8_t colorspace; // 0 = sRGB with linear alpha, 1 = all channels linear
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};
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Images are encoded row by row, left to right, top to bottom. The decoder and
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encoder start with {r: 0, g: 0, b: 0, a: 255} as the previous pixel value. An
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Images are encoded row by row, left to right, top to bottom. The decoder and
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encoder start with {r: 0, g: 0, b: 0, a: 255} as the previous pixel value. An
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image is complete when all pixels specified by width * height have been covered.
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Pixels are encoded as
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@ -101,20 +101,20 @@ Pixels are encoded as
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- a difference to the previous pixel value in r,g,b
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- full r,g,b or r,g,b,a values
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The color channels are assumed to not be premultiplied with the alpha channel
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The color channels are assumed to not be premultiplied with the alpha channel
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("un-premultiplied alpha").
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A running array[64] (zero-initialized) of previously seen pixel values is
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A running array[64] (zero-initialized) of previously seen pixel values is
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maintained by the encoder and decoder. Each pixel that is seen by the encoder
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and decoder is put into this array at the position formed by a hash function of
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the color value. In the encoder, if the pixel value at the index matches the
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current pixel, this index position is written to the stream as QOI_OP_INDEX.
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current pixel, this index position is written to the stream as QOI_OP_INDEX.
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The hash function for the index is:
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index_position = (r * 3 + g * 5 + b * 7 + a * 11) % 64
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Each chunk starts with a 2- or 8-bit tag, followed by a number of data bits. The
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bit length of chunks is divisible by 8 - i.e. all chunks are byte aligned. All
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Each chunk starts with a 2- or 8-bit tag, followed by a number of data bits. The
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bit length of chunks is divisible by 8 - i.e. all chunks are byte aligned. All
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values encoded in these data bits have the most significant bit on the left.
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The 8-bit tags have precedence over the 2-bit tags. A decoder must check for the
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@ -136,10 +136,10 @@ The possible chunks are:
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6-bit index into the color index array: 0..63
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A valid encoder must not issue 7 or more consecutive QOI_OP_INDEX chunks to the
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index 0, to avoid confusion with the 8 byte end marker.
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index 0, to avoid confusion with the 8 byte end marker.
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.- QOI_OP_DIFF -----------.
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.- QOI_OP_DIFF -----------.
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| Byte[0] |
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| 7 6 5 4 3 2 1 0 |
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|-------+-----+-----+-----|
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@ -150,16 +150,16 @@ index 0, to avoid confusion with the 8 byte end marker.
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2-bit green channel difference from the previous pixel between -2..1
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2-bit blue channel difference from the previous pixel between -2..1
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The difference to the current channel values are using a wraparound operation,
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The difference to the current channel values are using a wraparound operation,
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so "1 - 2" will result in 255, while "255 + 1" will result in 0.
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Values are stored as unsigned integers with a bias of 2. E.g. -2 is stored as
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Values are stored as unsigned integers with a bias of 2. E.g. -2 is stored as
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0 (b00). 1 is stored as 3 (b11).
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The alpha value remains unchanged from the previous pixel.
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.- QOI_OP_LUMA -------------------------------------.
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.- QOI_OP_LUMA -------------------------------------.
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| Byte[0] | Byte[1] |
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| 7 6 5 4 3 2 1 0 | 7 6 5 4 3 2 1 0 |
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|-------+-----------------+-------------+-----------|
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@ -170,16 +170,16 @@ The alpha value remains unchanged from the previous pixel.
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4-bit red channel difference minus green channel difference -8..7
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4-bit blue channel difference minus green channel difference -8..7
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The green channel is used to indicate the general direction of change and is
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The green channel is used to indicate the general direction of change and is
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encoded in 6 bits. The red and blue channels (dr and db) base their diffs off
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of the green channel difference and are encoded in 4 bits. I.e.:
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dr_dg = (last_px.r - cur_px.r) - (last_px.g - cur_px.g)
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db_dg = (last_px.b - cur_px.b) - (last_px.g - cur_px.g)
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The difference to the current channel values are using a wraparound operation,
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The difference to the current channel values are using a wraparound operation,
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so "10 - 13" will result in 253, while "250 + 7" will result in 1.
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Values are stored as unsigned integers with a bias of 32 for the green channel
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Values are stored as unsigned integers with a bias of 32 for the green channel
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and a bias of 8 for the red and blue channel.
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The alpha value remains unchanged from the previous pixel.
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@ -194,8 +194,8 @@ The alpha value remains unchanged from the previous pixel.
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2-bit tag b11
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6-bit run-length repeating the previous pixel: 1..62
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The run-length is stored with a bias of -1. Note that the run-lengths 63 and 64
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(b111110 and b111111) are illegal as they are occupied by the QOI_OP_RGB and
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The run-length is stored with a bias of -1. Note that the run-lengths 63 and 64
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(b111110 and b111111) are illegal as they are occupied by the QOI_OP_RGB and
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QOI_OP_RGBA tags.
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@ -238,15 +238,15 @@ Header - Public functions */
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extern "C" {
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#endif
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/* A pointer to a qoi_desc struct has to be supplied to all of qoi's functions.
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It describes either the input format (for qoi_write and qoi_encode), or is
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/* A pointer to a qoi_desc struct has to be supplied to all of qoi's functions.
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It describes either the input format (for qoi_write and qoi_encode), or is
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filled with the description read from the file header (for qoi_read and
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qoi_decode).
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The colorspace in this qoi_desc is an enum where
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The colorspace in this qoi_desc is an enum where
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0 = sRGB, i.e. gamma scaled RGB channels and a linear alpha channel
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1 = all channels are linear
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You may use the constants QOI_SRGB or QOI_LINEAR. The colorspace is purely
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You may use the constants QOI_SRGB or QOI_LINEAR. The colorspace is purely
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informative. It will be saved to the file header, but does not affect
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en-/decoding in any way. */
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@ -262,11 +262,11 @@ typedef struct {
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#ifndef QOI_NO_STDIO
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/* Encode raw RGB or RGBA pixels into a QOI image and write it to the file
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system. The qoi_desc struct must be filled with the image width, height,
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number of channels (3 = RGB, 4 = RGBA) and the colorspace.
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/* Encode raw RGB or RGBA pixels into a QOI image and write it to the file
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system. The qoi_desc struct must be filled with the image width, height,
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number of channels (3 = RGB, 4 = RGBA) and the colorspace.
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The function returns 0 on failure (invalid parameters, or fopen or malloc
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The function returns 0 on failure (invalid parameters, or fopen or malloc
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failed) or the number of bytes written on success. */
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int qoi_write(const char *filename, const void *data, const qoi_desc *desc);
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@ -277,7 +277,7 @@ number of channels from the file header is used. If channels is 3 or 4 the
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output format will be forced into this number of channels.
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The function either returns NULL on failure (invalid data, or malloc or fopen
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failed) or a pointer to the decoded pixels. On success, the qoi_desc struct
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failed) or a pointer to the decoded pixels. On success, the qoi_desc struct
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will be filled with the description from the file header.
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The returned pixel data should be free()d after use. */
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@ -289,8 +289,8 @@ void *qoi_read(const char *filename, qoi_desc *desc, int channels);
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/* Encode raw RGB or RGBA pixels into a QOI image in memory.
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The function either returns NULL on failure (invalid parameters or malloc
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failed) or a pointer to the encoded data on success. On success the out_len
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The function either returns NULL on failure (invalid parameters or malloc
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failed) or a pointer to the encoded data on success. On success the out_len
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is set to the size in bytes of the encoded data.
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The returned qoi data should be free()d after use. */
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@ -300,8 +300,8 @@ void *qoi_encode(const void *data, const qoi_desc *desc, int *out_len);
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/* Decode a QOI image from memory.
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The function either returns NULL on failure (invalid parameters or malloc
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failed) or a pointer to the decoded pixels. On success, the qoi_desc struct
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The function either returns NULL on failure (invalid parameters or malloc
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failed) or a pointer to the decoded pixels. On success, the qoi_desc struct
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is filled with the description from the file header.
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The returned pixel data should be free()d after use. */
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@ -346,8 +346,8 @@ Implementation */
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#define QOI_HEADER_SIZE 14
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/* 2GB is the max file size that this implementation can safely handle. We guard
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against anything larger than that, assuming the worst case with 5 bytes per
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pixel, rounded down to a nice clean value. 400 million pixels ought to be
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against anything larger than that, assuming the worst case with 5 bytes per
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pixel, rounded down to a nice clean value. 400 million pixels ought to be
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enough for anybody. */
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#define QOI_PIXELS_MAX ((unsigned int)400000000)
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@ -391,8 +391,8 @@ void *qoi_encode(const void *data, const qoi_desc *desc, int *out_len) {
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return NULL;
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}
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max_size =
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desc->width * desc->height * (desc->channels + 1) +
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max_size =
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desc->width * desc->height * (desc->channels + 1) +
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QOI_HEADER_SIZE + sizeof(qoi_padding);
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p = 0;
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@ -418,7 +418,7 @@ void *qoi_encode(const void *data, const qoi_desc *desc, int *out_len) {
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px_prev.rgba.b = 0;
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px_prev.rgba.a = 255;
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px = px_prev;
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px_len = desc->width * desc->height * desc->channels;
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px_end = px_len - desc->channels;
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channels = desc->channels;
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@ -466,14 +466,14 @@ void *qoi_encode(const void *data, const qoi_desc *desc, int *out_len) {
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if (
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vr > -3 && vr < 2 &&
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vg > -3 && vg < 2 &&
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vg > -3 && vg < 2 &&
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vb > -3 && vb < 2
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) {
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bytes[p++] = QOI_OP_DIFF | (vr + 2) << 4 | (vg + 2) << 2 | (vb + 2);
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}
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else if (
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vg_r > -9 && vg_r < 8 &&
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vg > -33 && vg < 32 &&
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vg_r > -9 && vg_r < 8 &&
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vg > -33 && vg < 32 &&
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vg_b > -9 && vg_b < 8
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) {
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bytes[p++] = QOI_OP_LUMA | (vg + 32);
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@ -532,7 +532,7 @@ void *qoi_decode(const void *data, int size, qoi_desc *desc, int channels) {
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desc->colorspace = bytes[p++];
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if (
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desc->width == 0 || desc->height == 0 ||
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desc->width == 0 || desc->height == 0 ||
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desc->channels < 3 || desc->channels > 4 ||
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desc->colorspace > 1 ||
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header_magic != QOI_MAGIC ||
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@ -598,7 +598,7 @@ void *qoi_decode(const void *data, int size, qoi_desc *desc, int channels) {
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index[QOI_COLOR_HASH(px) % 64] = px;
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}
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if (channels == 4) {
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if (channels == 4) {
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*(qoi_rgba_t*)(pixels + px_pos) = px;
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}
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else {
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@ -627,11 +627,11 @@ int qoi_write(const char *filename, const void *data, const qoi_desc *desc) {
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if (!encoded) {
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fclose(f);
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return 0;
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}
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}
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fwrite(encoded, 1, size, f);
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fclose(f);
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QOI_FREE(encoded);
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return size;
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}
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