Created the base Writer object for all barcode encoding, then wrote a QR Code version. A Writer encodes a series of raw bytes into a 2D greyscale bitmap, represented by a ByteArray. This seems like a better container than MonochromeBitmapSource, because we may want shades of grey when encoding future formats. The next step is to hook this up to the Android client.

git-svn-id: https://zxing.googlecode.com/svn/trunk@716 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
dswitkin 2008-11-17 22:10:45 +00:00
parent 8d79ad7085
commit 8175e2cc25
10 changed files with 274 additions and 222 deletions

View file

@ -41,10 +41,7 @@
optimize="true"
debug="${generate-debug}"
deprecation="true"
fork="true">
<!-- TODO re-add this package -->
<exclude name="com/google/zxing/qrcode/encoder/**"/>
</javac>
fork="true"/>
<jar jarfile="core.jar" basedir="build">
<!-- These entries allow core.jar to function as an OSGi bundle, and also specifices
additional attributes for compatibility with BugLabs's BUG platform.

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@ -0,0 +1,42 @@
/*
* Copyright 2008 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.zxing;
import com.google.zxing.common.ByteMatrix;
import com.google.zxing.qrcode.QRCodeWriter;
import java.util.Hashtable;
public final class MultiFormatWriter implements Writer {
public ByteMatrix encode(byte[] contents, BarcodeFormat format, int width,
int height) throws Exception {
return encode(contents, format, width, height, null);
}
public ByteMatrix encode(byte[] contents, BarcodeFormat format, int width, int height,
Hashtable hints) throws Exception {
if (format == BarcodeFormat.QR_CODE) {
return new QRCodeWriter().encode(contents, format, width, height, hints);
} else {
throw new IllegalArgumentException("No encoder available for format " + format);
}
}
}

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@ -0,0 +1,48 @@
/*
* Copyright 2008 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.zxing;
import com.google.zxing.common.ByteMatrix;
import java.util.Hashtable;
public interface Writer {
/**
* Encode a barcode using the default settings.
*
* @param contents The raw contents to encode in the barcode
* @param format The barcode format to generate
* @param width The preferred width in pixels
* @param height The preferred height in pixels
* @return The generated barcode as a Matrix of unsigned bytes (0 == black, 255 == white)
*/
ByteMatrix encode(byte[] contents, BarcodeFormat format, int width, int height) throws Exception;
/**
*
* @param contents The raw contents to encode in the barcode
* @param format The barcode format to generate
* @param width The preferred width in pixels
* @param height The preferred height in pixels
* @param hints Additional parameters to supply to the encoder
* @return The generated barcode as a Matrix of unsigned bytes (0 == black, 255 == white)
*/
ByteMatrix encode(byte[] contents, BarcodeFormat format, int width, int height, Hashtable hints)
throws Exception;
}

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@ -14,10 +14,11 @@
* limitations under the License.
*/
package com.google.zxing.qrcode.encoder;
package com.google.zxing.common;
/**
* A class which wraps a 2D array.
* A class which wraps a 2D array of bytes. The default usage is signed. If you want to use it as a
* unsigned container, it's up to you to do byteValue & 0xff at each location.
*
* JAVAPORT: I'm not happy about the argument ordering throughout the file, as I always like to have
* the horizontal component first, but this is for compatibility with the C++ code. The original
@ -26,13 +27,13 @@ package com.google.zxing.qrcode.encoder;
*
* @author dswitkin@google.com (Daniel Switkin)
*/
public final class Matrix {
public final class ByteMatrix {
private final byte[][] bytes;
private final int height;
private final int width;
public Matrix(int height, int width) {
public ByteMatrix(int height, int width) {
bytes = new byte[height][width];
this.height = height;
this.width = width;
@ -50,6 +51,10 @@ public final class Matrix {
return bytes[y][x];
}
public final byte[][] getArray() {
return bytes;
}
public final void set(int y, int x, byte value) {
bytes[y][x] = value;
}

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@ -0,0 +1,133 @@
/*
* Copyright 2008 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.zxing.qrcode;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.Writer;
import com.google.zxing.common.ByteMatrix;
import com.google.zxing.qrcode.encoder.ByteArray;
import com.google.zxing.qrcode.encoder.Encoder;
import com.google.zxing.qrcode.encoder.QRCode;
import java.util.Hashtable;
public final class QRCodeWriter implements Writer {
public ByteMatrix encode(byte[] contents, BarcodeFormat format, int width,
int height) throws Exception {
return encode(contents, format, width, height, null);
}
public ByteMatrix encode(byte[] contents, BarcodeFormat format, int width, int height,
Hashtable hints) throws Exception {
if (contents == null || contents.length == 0) {
throw new IllegalArgumentException("Found empty contents");
}
if (format != BarcodeFormat.QR_CODE) {
throw new IllegalArgumentException("Can only encode QR_CODE, but got " + format);
}
if (width < 0 || height < 0) {
throw new IllegalArgumentException("Requested dimensions are too small: " + width + "x" +
height);
}
// TODO: Check hints for error correction level instead of hardcoding
int errorCorrectionLevel = QRCode.EC_LEVEL_L;
QRCode code = new QRCode();
if (Encoder.Encode(new ByteArray(contents), errorCorrectionLevel, code)) {
return renderResult(code, width, height);
} else {
throw new IllegalStateException("Could not generate a QR Code");
}
}
// Note that the input matrix uses 0 == white, 1 == black, while the output matrix uses
// 0 == black, 255 == white (i.e. an 8 bit greyscale bitmap).
private ByteMatrix renderResult(QRCode code, final int width, final int height) {
ByteMatrix input = code.matrix();
int inputWidth = input.width();
int inputHeight = input.height();
int outputWidth = Math.max(width, inputWidth);
int outputHeight = Math.max(height, inputHeight);
int multiple = Math.min(outputWidth / inputWidth, outputHeight / inputHeight);
int leftPadding = (outputWidth - (inputWidth * multiple)) / 2;
int topPadding = (outputHeight - (inputHeight * multiple)) / 2;
ByteMatrix output = new ByteMatrix(outputHeight, outputWidth);
byte[][] outputArray = output.getArray();
// We could be tricky and use the first row in each set of multiple as the temporary storage,
// instead of allocating this separate array.
byte[] row = new byte[outputWidth];
// 1. Write the white lines at the top
for (int y = 0; y < topPadding; y++) {
setRowColor(outputArray[y], (byte) 255);
}
// 2. Expand the QR image to the multiple
final byte[][] inputArray = input.getArray();
for (int y = 0; y < inputHeight; y++) {
// a. Write the white pixels at the left of each row
for (int x = 0; x < leftPadding; x++) {
row[x] = (byte) 255;
}
// b. Write the contents of this row of the barcode
int offset = leftPadding;
for (int x = 0; x < inputWidth; x++) {
byte value = (inputArray[y][x] == 1) ? 0 : (byte) 255;
for (int z = 0; z < multiple; z++) {
row[offset + z] = value;
}
offset += multiple;
}
// c. Write the white pixels at the right of each row
offset = leftPadding + (inputWidth * multiple);
for (int x = offset; x < outputWidth; x++) {
row[x] = (byte) 255;
}
// d. Write the completed row multiple times
offset = topPadding + (y * multiple);
for (int z = 0; z < multiple; z++) {
System.arraycopy(row, 0, outputArray[offset + z], 0, outputWidth);
}
}
// 3. Write the white lines at the bottom
int offset = topPadding + (inputHeight * multiple);
for (int y = offset; y < outputHeight; y++) {
setRowColor(outputArray[y], (byte) 255);
}
return output;
}
private static void setRowColor(byte[] row, byte value) {
for (int x = 0; x < row.length; x++) {
row[x] = value;
}
}
}

View file

@ -18,6 +18,7 @@ package com.google.zxing.qrcode.encoder;
import com.google.zxing.common.reedsolomon.ReedSolomonEncoder;
import com.google.zxing.common.reedsolomon.GF256;
import com.google.zxing.common.ByteMatrix;
import java.util.Vector;
@ -341,7 +342,7 @@ private static final ECPolyInfo kECPolynomials[] = {
qr_code.num_rs_blocks(), final_bits);
// Step 7: Choose the mask pattern and set to "qr_code".
Matrix matrix = new Matrix(qr_code.matrix_width(), qr_code.matrix_width());
ByteMatrix matrix = new ByteMatrix(qr_code.matrix_width(), qr_code.matrix_width());
qr_code.set_mask_pattern(ChooseMaskPattern(final_bits, qr_code.ec_level(), qr_code.version(),
matrix));
if (qr_code.mask_pattern() == -1) {
@ -405,7 +406,7 @@ private static final ECPolyInfo kECPolynomials[] = {
}
private static int ChooseMaskPattern(final BitVector bits, int ec_level, int version,
Matrix matrix) {
ByteMatrix matrix) {
if (!QRCode.IsValidMatrixWidth(matrix.width())) {
Debug.LOG_ERROR("Invalid matrix width: " + matrix.width());
return -1;

View file

@ -16,6 +16,8 @@
package com.google.zxing.qrcode.encoder;
import com.google.zxing.common.ByteMatrix;
/**
* @author satorux@google.com (Satoru Takabayashi) - creator
* @author dswitkin@google.com (Daniel Switkin) - ported from C++
@ -24,7 +26,7 @@ public final class MaskUtil {
// The mask penalty calculation is complicated. See Table 21 of JISX0510:2004 (p.45) for details.
// Basically it applies four rules and summate all penalties.
public static int CalculateMaskPenalty(final Matrix matrix) {
public static int CalculateMaskPenalty(final ByteMatrix matrix) {
int penalty = 0;
penalty += ApplyMaskPenaltyRule1(matrix);
penalty += ApplyMaskPenaltyRule2(matrix);
@ -35,7 +37,7 @@ public final class MaskUtil {
// Apply mask penalty rule 1 and return the penalty. Find repetitive cells with the same color and
// give penalty to them. Example: 00000 or 11111.
public static int ApplyMaskPenaltyRule1(final Matrix matrix) {
public static int ApplyMaskPenaltyRule1(final ByteMatrix matrix) {
final int penalty = (ApplyMaskPenaltyRule1Internal(matrix, true) +
ApplyMaskPenaltyRule1Internal(matrix, false));
Debug.LOG_INFO("\tApplyMaskPenaltyRule1: " + penalty);
@ -45,8 +47,8 @@ public final class MaskUtil {
// Apply mask penalty rule 2 and return the penalty. Find 2x2 blocks with the same color and give
// penalty to them.
//
// JAVAPORT: Consider using Matrix.getArray() instead.
public static int ApplyMaskPenaltyRule2(final Matrix matrix) {
// JAVAPORT: Consider using ByteMatrix.getArray() instead.
public static int ApplyMaskPenaltyRule2(final ByteMatrix matrix) {
int penalty = 0;
for (int y = 0; y < matrix.height() - 1; ++y) {
for (int x = 0; x < matrix.width() - 1; ++x) {
@ -66,9 +68,9 @@ public final class MaskUtil {
// 10111010000, and give penalty to them. If we find patterns like 000010111010000, we give
// penalties twice (i.e. 40 * 2).
//
// JAVAPORT: This many calls to Matrix.get() looks expensive. We should profile and consider
// adding a byte[][] Matrix.getArray() method, then using that array locally.
public static int ApplyMaskPenaltyRule3(final Matrix matrix) {
// JAVAPORT: This many calls to ByteMatrix.get() looks expensive. We should profile and consider
// adding a byte[][] ByteMatrix.getArray() method, then using that array locally.
public static int ApplyMaskPenaltyRule3(final ByteMatrix matrix) {
int penalty = 0;
for (int y = 0; y < matrix.height(); ++y) {
for (int x = 0; x < matrix.width(); ++x) {
@ -128,7 +130,7 @@ public final class MaskUtil {
// - 55% => 10
// - 55% => 20
// - 100% => 100
public static int ApplyMaskPenaltyRule4(final Matrix matrix) {
public static int ApplyMaskPenaltyRule4(final ByteMatrix matrix) {
int num_dark_cells = 0;
for (int y = 0; y < matrix.height(); ++y) {
for (int x = 0; x < matrix.width(); ++x) {
@ -174,7 +176,7 @@ public final class MaskUtil {
// Helper function for ApplyMaskPenaltyRule1. We need this for doing this calculation in both
// vertical and horizontal orders respectively.
private static int ApplyMaskPenaltyRule1Internal(final Matrix matrix, boolean is_horizontal) {
private static int ApplyMaskPenaltyRule1Internal(final ByteMatrix matrix, boolean is_horizontal) {
int penalty = 0;
int num_same_bit_cells = 0;
int prev_bit = -1;

View file

@ -16,6 +16,8 @@
package com.google.zxing.qrcode.encoder;
import com.google.zxing.common.ByteMatrix;
/**
* @author satorux@google.com (Satoru Takabayashi) - creator
* @author dswitkin@google.com (Daniel Switkin) - ported from C++
@ -121,15 +123,15 @@ public final class MatrixUtil {
// Set all cells to -1. -1 means that the cell is empty (not set yet).
//
// JAVAPORT: We shouldn't need to do this at all. The code should be rewritten to begin encoding
// with the Matrix initialized all to zero.
public static void ClearMatrix(Matrix matrix) {
// with the ByteMatrix initialized all to zero.
public static void ClearMatrix(ByteMatrix matrix) {
matrix.clear((byte) -1);
}
// Build 2D matrix of QR Code from "data_bits" with "ec_level", "version" and "mask_pattern". On
// success, store the result in "matrix" and return true. On error, return false.
public static boolean BuildMatrix(final BitVector data_bits, int ec_level, int version,
int mask_pattern, Matrix matrix) {
int mask_pattern, ByteMatrix matrix) {
MatrixUtil.ClearMatrix(matrix);
if (!EmbedBasicPatterns(version, matrix)) {
return false;
@ -152,7 +154,7 @@ public final class MatrixUtil {
// - Timing patterns
// - Dark dot at the left bottom corner
// - Position adjustment patterns, if need be
public static boolean EmbedBasicPatterns(int version, Matrix matrix) {
public static boolean EmbedBasicPatterns(int version, ByteMatrix matrix) {
// Let's get started with embedding big squares at corners.
EmbedPositionDetectionPatternsAndSeparators(matrix);
// Then, embed the dark dot at the left bottom corner.
@ -166,7 +168,7 @@ public final class MatrixUtil {
}
// Embed type information. On success, modify the matrix and return true. On error, return false.
public static boolean EmbedTypeInfo(int ec_level, int mask_pattern, Matrix matrix) {
public static boolean EmbedTypeInfo(int ec_level, int mask_pattern, ByteMatrix matrix) {
BitVector type_info_bits = new BitVector();
if (!MakeTypeInfoBits(ec_level, mask_pattern, type_info_bits)) {
return false;
@ -201,7 +203,7 @@ public final class MatrixUtil {
// Embed version information if need be. On success, modify the matrix and return true. On error,
// return false. See 8.10 of JISX0510:2004 (p.47) for how to embed version information. Return
// true on success, otherwise return false.
public static boolean MaybeEmbedVersionInfo(int version, Matrix matrix) {
public static boolean MaybeEmbedVersionInfo(int version, ByteMatrix matrix) {
if (version < 7) { // Version info is necessary if version >= 7.
return true; // Don't need version info.
}
@ -229,7 +231,7 @@ public final class MatrixUtil {
// Embed "data_bits" using "mask_pattern". On success, modify the matrix and return true. On
// error, return false. For debugging purposes, it skips masking process if "mask_pattern" is -1.
// See 8.7 of JISX0510:2004 (p.38) for how to embed data bits.
public static boolean EmbedDataBits(final BitVector data_bits, int mask_pattern, Matrix matrix) {
public static boolean EmbedDataBits(final BitVector data_bits, int mask_pattern, ByteMatrix matrix) {
int bit_index = 0;
int direction = -1;
// Start from the right bottom cell.
@ -387,7 +389,7 @@ public final class MatrixUtil {
value == 1); // Dark (black).
}
private static void EmbedTimingPatterns(Matrix matrix) {
private static void EmbedTimingPatterns(ByteMatrix matrix) {
// -8 is for skipping position detection patterns (size 7), and two horizontal/vertical
// separation patterns (size 1). Thus, 8 = 7 + 1.
for (int i = 8; i < matrix.width() - 8; ++i) {
@ -406,13 +408,13 @@ public final class MatrixUtil {
}
// Embed the lonely dark dot at left bottom corner. JISX0510:2004 (p.46)
private static void EmbedDarkDotAtLeftBottomCorner(Matrix matrix) {
private static void EmbedDarkDotAtLeftBottomCorner(ByteMatrix matrix) {
Debug.DCHECK(matrix.get(matrix.height() - 8, 8) != 0);
matrix.set(matrix.height() - 8, 8, 1);
}
private static void EmbedHorizontalSeparationPattern(final int x_start, final int y_start,
Matrix matrix) {
ByteMatrix matrix) {
// We know the width and height.
Debug.DCHECK_EQ(8, kHorizontalSeparationPattern[0].length);
Debug.DCHECK_EQ(1, kHorizontalSeparationPattern.length);
@ -423,7 +425,7 @@ public final class MatrixUtil {
}
private static void EmbedVerticalSeparationPattern(final int x_start, final int y_start,
Matrix matrix) {
ByteMatrix matrix) {
// We know the width and height.
Debug.DCHECK_EQ(1, kVerticalSeparationPattern[0].length);
Debug.DCHECK_EQ(7, kVerticalSeparationPattern.length);
@ -437,7 +439,7 @@ public final class MatrixUtil {
// almost identical, since we cannot write a function that takes 2D arrays in different sizes in
// C/C++. We should live with the fact.
private static void EmbedPositionAdjustmentPattern(final int x_start, final int y_start,
Matrix matrix) {
ByteMatrix matrix) {
// We know the width and height.
Debug.DCHECK_EQ(5, kPositionAdjustmentPattern[0].length);
Debug.DCHECK_EQ(5, kPositionAdjustmentPattern.length);
@ -450,7 +452,7 @@ public final class MatrixUtil {
}
private static void EmbedPositionDetectionPattern(final int x_start, final int y_start,
Matrix matrix) {
ByteMatrix matrix) {
// We know the width and height.
Debug.DCHECK_EQ(7, kPositionDetectionPattern[0].length);
Debug.DCHECK_EQ(7, kPositionDetectionPattern.length);
@ -463,7 +465,7 @@ public final class MatrixUtil {
}
// Embed position detection patterns and surrounding vertical/horizontal separators.
private static void EmbedPositionDetectionPatternsAndSeparators(Matrix matrix) {
private static void EmbedPositionDetectionPatternsAndSeparators(ByteMatrix matrix) {
// Embed three big squares at corners.
final int pdp_width = kPositionDetectionPattern[0].length;
// Left top corner.
@ -495,7 +497,7 @@ public final class MatrixUtil {
}
// Embed position adjustment patterns if need be.
private static void MaybeEmbedPositionAdjustmentPatterns(final int version, Matrix matrix) {
private static void MaybeEmbedPositionAdjustmentPatterns(final int version, ByteMatrix matrix) {
if (version < 2) { // The patterns appear if version >= 2
return;
}

View file

@ -16,6 +16,8 @@
package com.google.zxing.qrcode.encoder;
import com.google.zxing.common.ByteMatrix;
/**
* @author satorux@google.com (Satoru Takabayashi) - creator
* @author dswitkin@google.com (Daniel Switkin) - ported from C++
@ -49,7 +51,7 @@ public final class QRCode {
private int num_data_bytes_;
private int num_ec_bytes_;
private int num_rs_blocks_;
private Matrix matrix_;
private ByteMatrix matrix_;
// They call encoding "mode". The modes are defined in 8.3 of JISX0510:2004 (p.14). It's unlikely
@ -106,7 +108,7 @@ public final class QRCode {
public int ec_level() { return ec_level_; }
// Version of the QR Code. The bigger size, the bigger version.
public int version() { return version_; }
// Matrix width of the QR Code.
// ByteMatrix width of the QR Code.
public int matrix_width() { return matrix_width_; }
// Mask pattern of the QR Code.
public int mask_pattern() { return mask_pattern_; }
@ -118,8 +120,8 @@ public final class QRCode {
public int num_ec_bytes() { return num_ec_bytes_; }
// Number of Reedsolomon blocks in the QR Code.
public int num_rs_blocks() { return num_rs_blocks_; }
// Matrix data of the QR Code.
public final Matrix matrix() { return matrix_; }
// ByteMatrix data of the QR Code.
public final ByteMatrix matrix() { return matrix_; }
// Return the value of the module (cell) pointed by "x" and "y" in the matrix of the QR Code. They
// call cells in the matrix "modules". 1 represents a black cell, and 0 represents a white cell.
@ -152,7 +154,7 @@ public final class QRCode {
IsValidMatrixWidth(matrix_width_) &&
IsValidMaskPattern(mask_pattern_) &&
num_total_bytes_ == num_data_bytes_ + num_ec_bytes_ &&
// Matrix stuff.
// ByteMatrix stuff.
matrix_ != null &&
matrix_width_ == matrix_.width() &&
// See 7.3.1 of JISX0510:2004 (p.5).
@ -230,7 +232,7 @@ public final class QRCode {
// This takes ownership of the 2D array. The 2D array will be
// deleted in the destructor of the class.
public void set_matrix(Matrix value) {
public void set_matrix(ByteMatrix value) {
matrix_ = value;
}
@ -360,8 +362,8 @@ public final class QRCode {
//
// JAVAPORT: This is going to be super expensive and unnecessary, we should not call this in
// production. I'm leaving it because it may be useful for testing. It should be removed entirely
// if Matrix is changed never to contain a -1.
private static boolean EverythingIsBinary(final Matrix matrix) {
// if ByteMatrix is changed never to contain a -1.
private static boolean EverythingIsBinary(final ByteMatrix matrix) {
for (int y = 0; y < matrix.height(); ++y) {
for (int x = 0; x < matrix.width(); ++x) {
int value = matrix.get(y, x);

View file

@ -1,180 +0,0 @@
/*
* Copyright 2008 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.zxing.qrcode.encoder;
// #include "third_party/png/png.h"
/**
* JAVAPORT: This class may get thrown out in the future, or it may turn into the object which
* returns a MonochromeBitmapSource.
*
* @author satorux@google.com (Satoru Takabayashi) - creator
* @author dswitkin@google.com (Daniel Switkin) - ported from C++
*/
public final class Renderer {
// See 7.3.7 of JISX0510:2004 (p. 11).
private static final int kQuietZoneSize = 4;
// Render QR Code as PNG image with "cell_size". On success, store
// the result in "result" and return true. On error, return false.
// The recommended cell size for desktop screens is 3. This
// setting generates 87x87 pixels PNG image for version 1 QR Code
// (21x21). 87 = (21 + 4 + 4) * 3. 4 is for surrounding white
// space (they call it quiet zone).
// Sorry for the long function but libpng's API is a bit complecated.
// See http://www.libpng.org/pub/png/libpng-1.2.5-manual.html for
// details.
public static boolean RenderAsPNG(final QRCode &qr_code, int cell_size,
String *result) {
// First, clear the result String.
result.clear();
// Create PNG class.
png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
null, null, null);
if (png_ptr == null) {
Debug.LOG_ERROR("Unable to create png_strupctp");
return false;
}
// Create PNG info.
png_infop info_ptr = png_create_info_struct(png_ptr);
if (info_ptr == null) {
Debug.LOG_ERROR("Unable to create png_infop");
png_destroy_write_struct(&png_ptr, (png_infopp)null);
return false;
}
// Calculate the width of the resulting image. Note that the height
// is equal to the width (i.e. the resulting image is square).
final int image_width = (qr_code.matrix_width() +
kQuietZoneSize * 2) * cell_size;
// Since we use 1-bit color depth, we only need 1 bit per pixel.
final int num_bytes_in_row = image_width / 8 +
(image_width % 8 == 0 ? 0 : 1);
// We'll use this storage later but we should prepare this before
// setjmp() so that this will be deleted on error. Today's lesson
// is that RAII isn't reliable with setjmp/longjmp!
scoped_array<char> row(new char[num_bytes_in_row]);
// Erorr handling of libpng is a bit tricky. If something bad
// happens in libpng, they call longjmp() to get to here.
if (setjmp(png_ptr.jmpbuf)) {
Debug.LOG_ERROR("Something bad happened in libpng");
png_destroy_write_struct(&png_ptr, &info_ptr);
return false;
}
// Attach the pointer to the result String and the pointer to the
// writer function.
png_set_write_fn(png_ptr, static_cast<void*>(result), PNGWriter, null);
// Set the image information.
png_set_IHDR(png_ptr, info_ptr, image_width, image_width,
1, // The color depth is 1 (black and white).
PNG_COLOR_TYPE_GRAY,
PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_BASE,
PNG_FILTER_TYPE_BASE);
// Write the file header information.
png_write_info(png_ptr, info_ptr);
// Quiet zone at the top.
FillRowWithWhite(num_bytes_in_row, row.get());
WriteRowNumTimes(png_ptr, row.get(), kQuietZoneSize * cell_size);
// Fill data.
for (int y = 0; y < qr_code.matrix_width(); ++y) {
FillRowWithData(num_bytes_in_row, qr_code, y, cell_size, row.get());
WriteRowNumTimes(png_ptr, row.get(), cell_size);
}
// Quiet zone at the bottom.
FillRowWithWhite(num_bytes_in_row, row.get());
WriteRowNumTimes(png_ptr, row.get(), kQuietZoneSize * cell_size);
// Cleanups for libpng stuff.
png_write_end(png_ptr, info_ptr);
png_destroy_write_struct(&png_ptr, &info_ptr);
// Finally, it's all done!
return true;
}
// Similar to RenderAsPNG but it renders QR code from data in
// "bytes" with error correction level "ec_level". This is the
// friendliest function in the QR code library.
public static boolean RenderAsPNGFromData(final ByteArray& bytes, int ec_level, int cell_size,
String *result) {
QRCode qr_code;
if (!Encoder.Encode(bytes, ec_level, &qr_code)) {
return false;
}
return RenderAsPNG(qr_code, cell_size, result);
}
// Callback function which gets called by png_write_row().
private static void PNGWriter(png_structp png_ptr, png_bytep data, png_size_t length) {
String* out = static_cast<String*>(png_get_io_ptr(png_ptr));
out.append(reinterpret_cast<char*>(data), length);
}
// Fill all pixels in "row" with white.
private static void FillRowWithWhite(final int num_bytes_in_row, char *row) {
memset(row, 0xff, num_bytes_in_row);
}
// Set the bit in "row" pointed by "index" to 1 (1 is for white).
private static void SetBit(final int index, char *row) {
final int byte_index = index / 8;
final int bit_index = index % 8;
row[byte_index] |= 0x80 >> bit_index;
}
// Fill pixels in "row" with data in "qr_code".
private static void FillRowWithData(final int num_bytes_in_row,
final QRCode &qr_code,
final int y,
final int cell_size,
char *row) {
memset(row, 0, num_bytes_in_row); // Fill all pixels with black.
int index = 0;
for (int i = 0; i < kQuietZoneSize * cell_size; ++i) {
SetBit(index++, row); // Cells in the quite zone should be white.
}
for (int x = 0; x < qr_code.matrix_width(); ++x) {
for (int i = 0; i < cell_size; ++i) {
if (qr_code.at(x, y) == 0) { // White cell.
SetBit(index, row);
}
++index;
}
}
for (int i = 0; i < kQuietZoneSize * cell_size; ++i) {
SetBit(index++, row);
}
}
// Write pixels in "row" to "png_ptr" "num" times.
private static void WriteRowNumTimes(png_structp png_ptr, char *row, final int num) {
for (int i = 0; i < num; ++i) {
png_write_row(png_ptr, reinterpret_cast<png_bytep>(row));
}
}
}